Method for Producing Molded Silicone Rubber Products Using Liquid Silicone Rubber

ABSTRACT

Described is a method for producing a molded silicone rubber product using a liquid silicone rubber (LSR) base comprising at least one vinyl siloxane polymer, at least one hydride crosslinker, and optionally at least one injection molding inhibitor. The single LSR base is fed into a feed line, and into the feed line are fed an inhibitor master batch comprising at least one liquid injection molding inhibitor and at least one vinyl siloxane polymer, and a catalyst master batch comprising at least one catalyst and at least one vinyl siloxane polymer. The invention is further directed to: said LSR base; said inhibitor master batch; said catalyst master batch; and a molded silicone rubber article produced by the methods and compositions described herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Non-Provisional Patent Application claims the benefit of U.S.Provisional Patent Application No. 61/207,855, filed on Jul. 30, 2008,and of U.S. Provisional Patent Application No. 61/175,614, filed on May5, 2009, each of which is hereby incorporated by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to method of preparing molded silicone rubberproducts using liquid silicone rubber (LSR). In particular, theinvention uses a new liquid silicone rubber composition and process toproduce cured silicone rubber products faster, with less equipment andless product variability.

2. Description of Related Art

Processes using liquid silicone rubbers (LSR) to form molded siliconerubber products have been around for almost four decades. Liquidsilicone rubbers belong to the group of heat-curing rubbers. Acharacteristic feature is their low viscosity during processing comparedto solid silicones or elastomers. Two-component mixtures increasinglycrosslink by the addition process. This means that the reaction takesplace without any decomposition product forming. This is an importantbenefit for the injection molding field since there are no byproducts ofcure, there is no concern of deposits forming on the molds.

Typically, a two part platinum catalyzed addition cure reaction is usedto make LSR molded rubber products, wherein the first component is amixture of vinylsiloxane polymers, treated amorphous fumed silica, andplatinum catalyst (component A) and the second component is a mixture ofvinylsiloxane polymers, treated amorphous fumed silica, hydrogensiloxane crosslinking polymers, and a cure rate inhibitor (component B).

The A and B components are separately pumped and metered through astatic mixer. The A and B mixture is further mixed in the LSR machinetransferring screw prior to injection into the mold. The A and B mixtureis then heat cured at a specific time and temperature depending on thepart size. The finished cured product is automatically ejected from themold, and the process repeated.

U.S. Pat. No. 3,884,866 discloses a two part LSR process using twodifferent vinylsiloxane polymers, a platinum catalyst, and pre-treatedsilica filler for the first component, and the same vinylsiloxanepolymers and pretreated silica filler plus a hydrogen containingpolysiloxane and cure rate inhibitor as the second component. U.S. Pat.No. 4,162,243 discloses a two part LSR process using an in situ treatedamorphous silica filler. U.S. Pat. No. 5,977,220 discloses a two partLSR process using a nitrogen organic cation salt to improve thecompression set of the silicone mixture. U.S. Pat. No. 6,034,199discloses a two part LSR process with improved cure rate inhibitors.U.S. Pat. No. 6,464,923 discloses a three part LSR process. The firstcomponent is a diorganopolysiloxane polymer and inorganic filler; thesecond component is a liquid catalyst and diorganopolysiloxane polymermixture; and the third component is hydrogen siloxane mixed with anorganopolysiloxane polymer. The patent also discloses the use of carbonblack as an inorganic filler. The three separate parts result inimproved storage stability over a two part LSR process.

BRIEF SUMMARY OF THE INVENTION

There are several problems in the two part LSR process. The first ispotential for the off ratio metering and mixing of the two separatecomponents, which results in unbalanced amounts of silicone hydridecrosslinker present in the finished products. This can result in erraticinjection cure rates and cured parts with variable physical properties.The second problem is the need for expensive equipment to pump the twoseparate mixtures into the metering and mixing device, plus the need fora metering and mixing devices at all. A third problem is the large andspecific (non variable, or set) amount of inhibitor present in thesecond component that is required to obtain a multi-day room temperaturework life. The inhibitor level can slow down the cure rate of the moldedproduct.

The present invention provides improved processes suitable for themanufacture of molded silicone rubber products using LSR. The processuses a single LSR base comprising vinyl siloxane polymers, and siliconehydride cross linkers, but not catalyst. Optional base components mayinclude liquid injection molding inhibitors, additional vinyl siloxanepolymers, hydride crosslinkers, fillers, releasing agents, andpre-structuring compounds, but—again—not catalyst. The process alsocomprises a catalyst master batch comprising at least one catalyst andat least one vinyl siloxane polymer. The process may also comprise aninhibitor master batch comprising at least one liquid injection moldinginhibitor and at least one vinyl siloxane polymer.

The single base may then be fed into an injection molding machine (IMM)via one entry point, and the catalyst master batch may be fed into theIMM via a second entry point. Alternatively, the inhibitor master batchmay be fed into the IMM via a third entry point. The single base,catalyst master batch, and inhibitor master batch (if used) enter theIMM barrel via separate entry points and are mixed together by operationof the IMM.

Alternatively, the single base may be fed from a base storage tank intoa base feed line, wherein the base feed line conducts the base into thebarrel of an injection molding machine. An inhibitor master batchstorage tank may feed—via an injector—the inhibitor master batch intothe base feed line at a first point, and the catalyst master batchstorage tank may feed—via an injector—the catalyst master batch into thebase feed line at a second point, wherein the second point is betweenthe first point and the IMM barrel. Preferably, the catalyst masterbatch is fed into the base feed line at a point as close as possible tothe IMM barrel. In one variation of this process, the base feed linefeeds into the injection molding machine without any static or dynamicmixers in the line. In another variation, the base feed line feeds intoa first dynamic or static mixer located between the first point andbefore the second point. In another variation, the base feed line feedsinto a second dynamic or static mixer located between the second pointand IMM barrel. In yet another variation, the base feed line feeds intoa first dynamic or static mixer located between the first point andbefore the second point, and into a second dynamic or static mixerlocated between the second point and IMM barrel; the first and seconddynamic or static mixers may be, independently of one another, dynamicor static. In still another variation, the base feed line feeds into an“orifice,” which serves to temporarily constrict the flow of materialthrough the base feed line and so cause localized turbulent mixing ordispersion. Without intending to be limited thereby, an exemplaryorifice useful with the present invention is approximately 0.125 inchesthick and possesses a circular opening about 0.1 inch in diameter, whichopening is less than the inner diameter of the base feed line.

Adjusting the injector shot size of the injectors is useful for adequatemixing of the components of the invention. “Injector shot size” is theamount of master batch (either inhibitor master batch or catalyst masterbatch) material injected into the stream (the stream of material in thebase feed line) each time the injector fires. The purpose of varying andcontrolling injector shot size is to ensure that the proper amount ofcatalyst and inhibitor are present in the base. “Mold shot size” is theamount of LSR material injected into the mold for each cycle ofproduction. The purpose of varying and controlling the mold shot size isto inject the appropriate amount of base, containing catalyst andinhibitor, into a heated metal cavity—the mold. For example, theinjector shot size may be from about 0.01 grams to about 0.25 grams, andpreferably from about 0.1 grams to about 0.15 grams. As will berecognized by those having ordinary skill in the art, the optimal moldshot size is a function of the size of the final molded product. Forexample, a smaller part may require only a few grams of the injectedmaterial per mold shot, so less of the injected material is requiredwith each shot. On the other hand, larger parts may require hundreds ofgrams of the injected material per mold shot, in which case more of theinjected material is required with each mold shot. In the event thatless of the injected material is injected into the stream, more frequentinjector shots (e.g., at least 2 shots per second at the lower injectorshot size range) may be required to achieve an appropriate amount ofinjected material. Similarly, in the event that more of the injectedmaterial is injected into the stream, less frequent injector shots maybe required. Thus, by controlling both the injector shot size and theinjection frequency one may enjoy significant control over the finalproduct.

The single base of the present invention reduces metering errorsassociated with mixing the vinyl siloxane and hydride cross linkersprior to injection into the mold, reduces cure time, and reducesequipment cost, all compared to a two part LSR process. Further, thestability or work-life of the LSR mixture in the injection moldingmachine is improved because the platinum catalyst is separatelycontrolled. Instead of the three- to five-day room temperature work liferesulting from standard two-part LSR techniques, the methods of thepresent invention yield an infinite room temperature pot life becausethe platinum catalyst feed (the platinum master batch feed, or “PtMBX”feed) may simply be turned off. Moreover, the present invention employsan inhibitor master batch (“Inhibitor MBX”), by which the molder cancontrol cure speed: smaller parts may be cured faster (using lowerinhibitor levels), and larger parts may be cured more slowly (usinghigher inhibitor levels), allowing the reliable manufacture ofperfect-quality parts by allowing the heated mold cavity to becompletely filled before curing. The principal improvements of theprocesses of the present invention center around the consistentproduction of high-quality molded parts and providing cure-speed controlto the molder. With the present invention, these advantages are achievedin part through control over the catalyst master batch (which may beturned on or off, the selection and maintenance of a constantvinyl:hydride ratio in the base, and selective control of the inhibitorlevel. The present invention stands in contrast to prior art standardtwo-part LSR processes which possess a predetermined cure speed that isdictated by the set inhibitor level, cannot be modified, and is subjectto vinyl:hydride ratio variation due to pumping variability.

Additional configurations may include: removing the inhibitor from thebase and feeding it directly into the mixer, and separately feeding aportion of the vinyl siloxane polymers into the mixer (e.g., with theinhibitor). These, and other configurations, are explained more fullybelow.

According to one aspect of the invention, a process is provided formaking molded silicone rubber products using a single LSR base.

In one embodiment, a method for producing a molded silicone rubberproduct is disclosed, the method comprising: a) feeding into a base feedline a liquid silicone rubber base comprising: i) at least one vinylsiloxane polymer; and ii) at least one hydride crosslinker; b) feedinginto a catalyst feed line a catalyst master batch comprising: i) atleast one catalyst; and ii) optionally, at least one vinyl siloxanepolymer; c) optionally feeding into an optional inhibitor feed line anoptional inhibitor master batch comprising: i) at least one liquidinjection molding inhibitor; and ii) optionally, at least one vinylsiloxane polymer; d) optionally feeding into an optional additive feedline an optional at least one additive; e) directing said liquidsilicone rubber base via said base feed line, and said catalyst masterbatch via said catalyst feed line, optionally directing said optionalinhibitor master batch via said optional inhibitor feed line, andoptionally directing said optional at least one additive via saidoptional additive feed line, into the barrel of an injection moldingmachine; F operating said injection molding machine, thereby mixing saidliquid silicone rubber base, said catalyst master batch, said optionalinhibitor master batch, and said optional at least one additive; and g)curing said mixed liquid silicone rubber base, catalyst master batch,optional inhibitor master batch, and optional at least one additive byheating.

In one aspect of this embodiment, the at least one vinyl siloxanepolymer of the liquid silicone rubber base, the catalyst master batch,and the optional inhibitor master batch are independently selected fromthe group consisting of Formula I-3, Formula I-4, Formula I-5, FormulaI-6, and Formula I-7, as defined below, and combinations thereof,wherein: the radical R are, independently, selected from the groupconsisting of monovalent hydrocarbon radicals and halogenated monovalenthydrocarbon radicals; the radical R¹ are, independently, selected fromthe group consisting of phenyl, lower alkenyl of 2 to 8 carbon atoms,lower alkyl of 1 to 8 carbon atoms and mononuclear aryl radicals; theradical R² are, independently, selected from the group consisting of analkyl radical, a mononuclear aryl radical, a lower alkyl radical of 1 to8 carbon atoms, a phenyl radical, lower alkenyl of 2 to 8 carbon atoms,and a vinyl group; the radical R″ are, independently, selected from thesame groups as the radical R¹; Vi denotes vinyl; m is an integer fromabout 100 to about 10,000; n is an integer from about 100 to about 400;o is an integer from about 2 to about 8; p is an integer from about 100to about 200; q is an integer from about 5 to about 15; w is an integerfrom about 0 to about 500; x is an integer from about 100 to about10,000; y is an integer from about 0 to about 300; and z is an integerfrom about 0 to about 200.

In another aspect of this embodiment, the at least one hydridecrosslinker is selected from the group consisting of: Formula II-3,Formula II-4, Formula II-5, Formula II-6, and Formula II-7, as definedbelow, and combinations thereof, wherein: each R⁴ is selected,independently, from the group consisting of hydrogen, monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals;each R⁵ radical is selected, independently, from the group consisting ofmonovalent hydrocarbon radicals, and halogenated monovalent hydrocarbonradicals; s is an integer from about 1 to about 1000; t is an integerfrom about 5 to about 200; u is an integer from about 14 to about 30; vis an integer from about 12 to about 21; w is an integer from about 2 toabout 8; x is an integer from about 3 to about 9; y is an integer fromabout 5 to about 15; M is monofunctional trimethylsilyl or(CH₃)₃SiO_(1/2); H is hydrogen; and Q is tetrafunctional silicon dioxideor SiO_(4/2). Preferably, at least three R⁴ groups of Formula II-3 arehydrogen.

In yet another aspect of this embodiment, the at least one catalyst is aplatinum complex formed from a reaction between H₂PtCl₆+6H₂O+ dimethylvinyl terminated polydimethylsiloxane polymer. Additionally, the atleast one liquid injection molding inhibitor of the optional inhibitormaster batch may be selected from the group consisting of: Formula III,Formula VI, and combinations thereof, wherein: a) R¹ has the formula ofFormula IV; b) R² is selected from the group consisting of Formula IV,hydrogen, triorganosilyl radicals, siloxanes, and Formula V; c) R³ isselected from the group consisting of: of divalent hydrocarbonradicalsconsisting of linear or branched alkyl radicals having from about 1 toabout 10 carbon atoms; linear or branched alkenyl radicals having fromabout 1 to about 10 carbon atoms; linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; cycloalkyl radicals havingfrom about 3 to about 12 carbon atoms; cycloalkenyl radicals having fromabout 3 to about 12 carbon atoms; cycloalkynyl radicals having fromabout 8 to about 16 carbon atoms; fluorinated linear or branched alkylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkyl radicals having from about 1 to about 10 carbonatoms; brominated linear or branched alkyl radicals having from about 1to about 10 carbon atoms; fluorinated linear or branched alkenylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkenyl radicals having from about 1 to about 10carbon atoms; brominated linear or branched alkenyl radicals having fromabout 1 to about 10 carbon atoms; fluorinated linear or branched alkynylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkynyl radicals having from about 1 to about 10carbon atoms; brominated linear or branched alkynyl radicals having fromabout 1 to about 10 carbon atoms; hydrocarbonoxy radicals containing atleast two carbon atoms; fluorinated hydrocarbonoxy radicals containingat least two carbon atoms; chlorinated hydrocarbonoxy radicalscontaining at least two carbon atoms; brominated hydrocarbonoxy radicalscontaining at least two carbon atoms; aryl radicals; linear or branchedalkyl aryl radicals; fluorinated aryl radicals; chlorinated arylradicals; brominated aryl radicals; fluorinated linear or branchedalkyl-, alkenyl-, or alkynyl aryl radicals; chlorinated linear orbranched alkyl-, alkenyl-, or alkynyl aryl radicals; and brominatedlinear or branched alkyl-, alkenyl-, or alkynyl aryl radicals; d) R⁴ isselected from the group of monovalent radicals consisting of: hydrogen,linear or branched alkyl radicals having from about 1 to about 10 carbonatoms; linear or branched alkenyl radicals having from about 1 to about10 carbon atoms; linear or branched alkynyl radicals having from about 1to about 10 carbon atoms; cycloalkyl radicals having from about 3 toabout 12 carbon atoms; cycloalkenyl radicals having from about 3 toabout 12 carbon atoms; cycloalkynyl radicals having from about 8 toabout 16 carbon atoms; fluorinated linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkyl radicals having from about 1 toabout 10 carbon atoms; fluorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; fluorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; hydrocarbonoxy radicals containing at least twocarbon atoms; fluorinated hydrocarbonoxy radicals containing at leasttwo carbon atoms; chlorinated hydrocarbonoxy radicals containing atleast two carbon atoms; brominated hydrocarbonoxy radicals containing atleast two carbon atoms aryl radicals; linear or branched alkyl arylradicals; fluorinated aryl radicals; chlorinated aryl radicals;brominated aryl radicals; fluorinated linear or branched alkyl-,alkenyl-, or alkynyl aryl radicals; chlorinated linear or branchedalkyl-, alkenyl-, or alkynyl aryl radicals; brominated linear orbranched alkyl-, alkenyl-, or alkynyl aryl radicals; and triorganosilylradicals; and e) R is selected from the group consisting of: hydrogen;alkyl; phenyl; and C_(x)H_(y), where x is an integer from about 2 toabout 10, and y is an integer from about 4 to about 21.

In a further aspect of this embodiment, the optional at least oneadditive is selected from the group consisting of color master batches,UV stabilizers, light stabilizers, self bonding additives,anti-microbial additives, thermal stabilizers, release agents,antistatic additives, flame proofing additives, low compression setadditives, durometer adjustment additives, oil resistance additives,anti-crepe hardening additives, mold release additives, plasticizers,thickening or consistency increase additives, blowing agents, andcombinations thereof.

In another aspect of this embodiment, the liquid silicone rubber basefurther comprises at least one filler, and the filler may be in situtreated fumed silica treated with hexamethyldisilazane andtetramethyldivinyldisilazane. Additionally, the liquid silicone rubberbase may further comprise at least one pre-structuring compound. Thepre-structuring compound may comprise Formula X, wherein R is selectedfrom the group consisting of monovalent hydrocarbon radicals, andhalogenated monovalent hydrocarbon radicals; and n is an integer fromabout 0 to about 12. The liquid silicone rubber base of this embodimentmay further comprise at least one release agent. The at least onerelease agent may have the formula M_(x)Q^(OH), wherein x is an integerfrom about 1 to about 3.

In a further aspect of this embodiment, the base feed line feeds intothe barrel of the injection molding machine, and said catalyst feed linefeeds into said base feed line, the liquid silicone rubber base mayfurther comprise at least one liquid injection molding inhibitor, andthe optional inhibitor feed line may feed into the base feed line.

In a further aspect of this embodiment, the base feed line feedsseparately into the barrel of the injection molding machine, thecatalyst feed line feeds separately into the barrel of the injectionmolding machine, the optional inhibitor feed line feeds separately intothe barrel of the injection molding machine, and the optional additivefeed line feeds separately into the barrel of the injection moldingmachine.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; and (2) at least one hydride crosslinker; (b) feedinginto said injection molding machine an inhibitor master batchcomprising: (1) at least one liquid injection molding inhibitor; and (2)at least one vinyl siloxane polymer; (c) feeding into said injectionmolding machine a catalyst master batch comprising: (1) at least onecatalyst; and (2) at least one vinyl siloxane polymer; (d) operatingsaid injection molding machine, thereby mixing said liquid siliconerubber base, said inhibitor master batch, and said catalyst masterbatch; and (e) curing said mixed liquid silicone rubber base, inhibitormaster batch, and catalyst master batch by heating. Optionally, theliquid silicone rubber base of step (a) may further comprise: (3) atleast one liquid injection molding inhibitor. Preferably, the optionalat least one liquid injection molding inhibitor of step (a) is presentin a trace amount.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; and (3) at leastone filler; (b) feeding into said injection molding machine an inhibitormaster batch comprising: (1) at least one liquid injection moldinginhibitor; and (2) at least one vinyl siloxane polymer; (c) feeding intosaid injection molding machine a catalyst master batch comprising: (1)at least one catalyst; and (2) at least one vinyl siloxane polymer; (d)operating said injection molding machine, thereby mixing said liquidsilicone rubber base, said inhibitor master batch, and said catalystmaster batch; and (e) curing said mixed liquid silicone rubber base,inhibitor master batch, and catalyst master batch by heating.Optionally, the liquid silicone rubber base of step (a) may furthercomprise: (4) at least one liquid injection molding inhibitor.Preferably, the optional at least one liquid injection molding inhibitorof step (a) is present in a trace amount.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; (3) at least onefiller; and (4) at least one pre-structuring compound; (b) feeding intosaid injection molding machine an inhibitor master batch comprising: (1)at least one liquid injection molding inhibitor; and (2) at least onevinyl siloxane polymer; (c) feeding into said injection molding machinea catalyst master batch comprising: (1) at least one catalyst; and (2)at least one vinyl siloxane polymer; (d) operating said injectionmolding machine, thereby mixing said liquid silicone rubber base, saidinhibitor master batch, and said catalyst master batch; and (e) curingsaid mixed liquid silicone rubber base, inhibitor master batch, andcatalyst master batch by heating. Optionally, the liquid silicone rubberbase of step (a) may further comprise: (5) at least one liquid injectionmolding inhibitor. Preferably, the optional at least one liquidinjection molding inhibitor of step (a) is present in a trace amount.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; (3) at least onefiller; (4) at least one pre-structuring compound; and (5) at least onesilicone release agent; (b) feeding into said injection molding machinean inhibitor master batch comprising: (1) at least one liquid injectionmolding inhibitor; and (2) at least one vinyl siloxane polymer; (c)feeding into said injection molding machine a catalyst master batchcomprising: (1) at least one catalyst; and (2) at least one vinylsiloxane polymer; (d) operating said injection molding machine, therebymixing said liquid silicone rubber base, said inhibitor master batch,and said catalyst master batch; and (e) curing said mixed liquidsilicone rubber base, inhibitor master batch, and catalyst master batchby heating. Optionally, the liquid silicone rubber base of step (a) mayfurther comprise: (6) at least one liquid injection molding inhibitor.Preferably, the optional at least one liquid injection molding inhibitorof step (a) is present in a trace amount.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; and (3) at leastone liquid injection molding inhibitor; (b) feeding into said injectionmolding machine a catalyst master batch comprising: (1) at least onecatalyst; and (2) at least one vinyl siloxane polymer; (c) operatingsaid injection molding machine, thereby mixing said liquid siliconerubber base and said catalyst master batch; and (d) curing said mixedliquid silicone rubber base and catalyst master batch by heating.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; (3) at least onefiller; and (4) at least one liquid injection molding inhibitor, into aninjection molding machine; (b) feeding into said injection moldingmachine a catalyst master batch comprising: (1) at least one catalyst;and (2) at least one vinyl siloxane polymer; (c) operating saidinjection molding machine, thereby mixing said liquid silicone rubberbase and said catalyst master batch; and (d) curing said mixed liquidsilicone rubber base and catalyst master batch by heating.

In a further embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into an injection moldingmachine a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; (3) at least onefiller; (4) at least one pre-structuring compound; and (5) at least oneliquid injection molding inhibitor, into an injection molding machine;(b) feeding into said injection molding machine a catalyst master batchcomprising: (1) at least one catalyst; and (2) at least one vinylsiloxane polymer; (c) operating said injection molding machine, therebymixing said liquid silicone rubber base and said catalyst master batch;and (d) curing said mixed liquid silicone rubber base and catalystmaster batch by heating.

In yet another embodiment, a method of producing a molded siliconerubber product is disclosed comprising: (a) feeding into an injectionmolding machine a liquid silicone rubber base comprising: (1) at leastone vinyl siloxane polymer; (2) at least one hydride crosslinker; (3) atleast one filler; (4) at least one pre-structuring compound; (5) atleast one silicone release agent; and (6) at least one liquid injectionmolding inhibitor, into an injection molding machine; (b) feeding intosaid injection molding machine a catalyst master batch comprising: (1)at least one catalyst; and (2) at least one vinyl siloxane polymer; (c)operating said injection molding machine, thereby mixing said liquidsilicone rubber base and said catalyst master batch; and (d) curing saidmixed liquid silicone rubber base and catalyst master batch by heating.

In yet a further embodiment, a method of producing a molded siliconerubber product is disclosed comprising: (a) feeding into a base feedline a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; and (2) at least one hydride crosslinker, wherein saidbase feed line feeds into the barrel of an injection molding machine;(b) feeding into said base feed line containing said liquid siliconerubber base an inhibitor master batch comprising: (1) at least oneliquid injection molding inhibitor; and (2) at least one vinyl siloxanepolymer; (c) feeding into said base feed line containing said liquidsilicone rubber base and said inhibitor master batch a catalyst masterbatch comprising: (1) at least one catalyst, and (2) at least one vinylsiloxane polymer; (d) transferring said liquid silicone rubber base,said inhibitor master batch, and said catalyst master batch into thebarrel of the injection molding machine via the base feed line; (e)operating said injection molding machine, thereby mixing said liquidsilicone rubber base, said inhibitor master batch, and said catalystmaster batch; and (F curing said mixed liquid silicone rubber base,inhibitor master batch, and catalyst master batch by heating. In oneaspect of this embodiment, the base feed line feeds into the injectionmolding machine without any static or dynamic mixers in the line. Inanother aspect of this embodiment, the base feed line feeds into adynamic or a static mixer between steps (b) and (c) above. In anotheraspect of this embodiment, the base feed line feeds into a dynamic or astatic mixer between steps (c) and (d) above. In yet another aspect ofthis embodiment, the base feed line feeds into a dynamic or a staticmixer between steps (b) and (c) above, and again between steps (c) and(d) above. Optionally, the liquid silicone rubber base of step (a) mayfurther comprise: (3) at least one liquid injection molding inhibitor.Preferably, the optional at least one liquid injection molding inhibitorof step (a) is present in a trace amount.

In another subsequent embodiment, a method for producing a moldedsilicone rubber product is disclosed comprising: (a) feeding into a basefeed line a liquid silicone rubber base comprising: (1) at least onevinyl siloxane polymer; (2) at least one hydride crosslinker; and (3) atleast one filler, wherein said base feed line feeds into the barrel ofan injection molding machine; (b) feeding into said base feed linecontaining said liquid silicone rubber base an inhibitor master batchcomprising: (1) at least one liquid injection molding inhibitor; and (2)at least one vinyl siloxane polymer; (c) feeding into said base feedline containing said liquid silicone rubber base and said inhibitormaster batch a catalyst master batch comprising: (1) at least onecatalyst, and (2) at least one vinyl siloxane polymer; (d) transferringsaid liquid silicone rubber base, said inhibitor master batch, and saidcatalyst master batch into the barrel of the injection molding machinevia the base feed line; (e) operating said injection molding machine,thereby mixing said liquid silicone rubber base, said inhibitor masterbatch, and said catalyst master batch; and (F curing said mixed liquidsilicone rubber base, inhibitor master batch, and catalyst master batchby heating. In one aspect of this embodiment, the base feed line feedsinto the injection molding machine without any static or dynamic mixersin the line. In another aspect of this embodiment, the base feed linefeeds into a dynamic or a static mixer between steps (b) and (c) above.In another aspect of this embodiment, the base feed line feeds into adynamic or a static mixer between steps (c) and (d) above. In yetanother aspect of this embodiment, the base feed line feeds into adynamic or a static mixer between steps (b) and (c) above, and againbetween steps (c) and (d) above. Optionally, the liquid silicone rubberbase of step (a) may further comprise: (4) at least one liquid injectionmolding inhibitor. Preferably, the optional at least one liquidinjection molding inhibitor of step (a) is present in a trace amount.

In another subsequent embodiment, a method for producing a moldedsilicone rubber product is disclosed comprising: (a) feeding into a basefeed line a liquid silicone rubber base comprising: (1) at least onevinyl siloxane polymer; (2) at least one hydride crosslinker; (3) atleast one filler; and (4) at least one pre-structuring compound, whereinsaid base feed line feeds into the barrel of an injection moldingmachine; (b) feeding into said base feed line containing said liquidsilicone rubber base an inhibitor master batch comprising: (1) at leastone liquid injection molding inhibitor; and (2) at least one vinylsiloxane polymer; (c) feeding into said base feed line containing saidliquid silicone rubber base and said inhibitor master batch a catalystmaster batch comprising: (1) at least one catalyst, and (2) at least onevinyl siloxane polymer; (d) transferring said liquid silicone rubberbase, said inhibitor master batch, and said catalyst master batch intothe barrel of the injection molding machine via the base feed line; (e)operating said injection molding machine, thereby mixing said liquidsilicone rubber base, said inhibitor master batch, and said catalystmaster batch; and (F curing said mixed liquid silicone rubber base,inhibitor master batch, and catalyst master batch by heating. In oneaspect of this embodiment, the base feed line feeds into the injectionmolding machine without any static or dynamic mixers in the line. Inanother aspect of this embodiment, the base feed line feeds into adynamic or a static mixer between steps (b) and (c) above. In anotheraspect of this embodiment, the base feed line feeds into a dynamic or astatic mixer between steps (c) and (d) above. In yet another aspect ofthis embodiment, the base feed line feeds into a dynamic or a staticmixer between steps (b) and (c) above, and again between steps (c) and(d) above. Optionally, the liquid silicone rubber base of step (a) mayfurther comprise: (5) at least one liquid injection molding inhibitor.Preferably, the optional at least one liquid injection molding inhibitorof step (a) is present in a trace amount.

In another subsequent embodiment, a method for producing a moldedsilicone rubber product is disclosed comprising: (a) feeding into a basefeed line a liquid silicone rubber base comprising: (1) at least onevinyl siloxane polymer; (2) at least one hydride crosslinker; (3) atleast one filler; (4) at least one pre-structuring compound; and (5) atleast one silicone release agent, wherein said base feed line feeds intothe barrel of an injection molding machine; (b) feeding into said basefeed line containing said liquid silicone rubber base an inhibitormaster batch comprising: (1) at least one liquid injection moldinginhibitor; and (2) at least one vinyl siloxane polymer; (c) feeding intosaid base feed line containing said liquid silicone rubber base and saidinhibitor master batch a catalyst master batch comprising: (1) at leastone catalyst, and (2) at least one vinyl siloxane polymer; (d)transferring said liquid silicone rubber base, said inhibitor masterbatch, and said catalyst master batch into the barrel of the injectionmolding machine via the base feed line; (e) operating said injectionmolding machine, thereby mixing said liquid silicone rubber base, saidinhibitor master batch, and said catalyst master batch; and (F curingsaid mixed liquid silicone rubber base, inhibitor master batch, andcatalyst master batch by heating. In one aspect of this embodiment, thebase feed line feeds into the injection molding machine without anystatic or dynamic mixers in the line. In another aspect of thisembodiment, the base feed line feeds into a dynamic or a static mixerbetween steps (b) and (c) above. In another aspect of this embodiment,the base feed line feeds into a dynamic or a static mixer between steps(c) and (d) above. In yet another aspect of this embodiment, the basefeed line feeds into a dynamic or a static mixer between steps (b) and(c) above, and again between steps (c) and (d) above. Optionally, theliquid silicone rubber base of step (a) may further comprise: (6) atleast one liquid injection molding inhibitor. Preferably, the optionalat least one liquid injection molding inhibitor of step (a) is presentin a trace amount.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into a base feed line aliquid silicone rubber base comprising: (1) at least one vinyl siloxanepolymer; (2) at least one hydride crosslinker; and (3) at least oneliquid injection molding inhibitor, wherein said base feed line feedsinto the barrel of an injection molding machine; (b) feeding into saidbase feed line containing said liquid silicone rubber base a catalystmaster batch comprising: (1) at least one catalyst; and (2) at least onevinyl siloxane polymer; (c) transferring said liquid silicone rubberbase and said catalyst master batch into the barrel of the injectionmolding machine via the base feed line; (d) operating said injectionmolding machine, thereby mixing said liquid silicone rubber base andsaid catalyst master batch; and (d) curing said mixed liquid siliconerubber base and catalyst master batch by heating. In one aspect of thisembodiment, the base feed line feeds into the injection molding machinewithout any static or dynamic mixers in the line. In another aspect ofthis embodiment, the base feed line feeds into a dynamic or a staticmixer between steps (b) and (c) above.

In another embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into a base feed line aliquid silicone rubber base comprising: (1) at least one vinyl siloxanepolymer; (2) at least one hydride crosslinker; (3) at least one filler;and (4) at least one liquid injection molding inhibitor, wherein saidbase feed line feeds into the barrel of an injection molding machine;(b) feeding into said base feed line containing said liquid siliconerubber base a catalyst master batch comprising: (1) at least onecatalyst; and (2) at least one vinyl siloxane polymer; (c) transferringsaid liquid silicone rubber base and said catalyst master batch into thebarrel of the injection molding machine via the base feed line; (d)operating said injection molding machine, thereby mixing said liquidsilicone rubber base and said catalyst master batch; and (e) curing saidmixed liquid silicone rubber base and catalyst master batch by heating.In one aspect of this embodiment, the base feed line feeds into theinjection molding machine without any static or dynamic mixers in theline. In another aspect of this embodiment, the base feed line feedsinto a dynamic or a static mixer between steps (b) and (c) above.

In a further embodiment, a method of producing a molded silicone rubberproduct is disclosed comprising: (a) feeding into a base feed line aliquid silicone rubber base comprising: (1) at least one vinyl siloxanepolymer; (2) at least one hydride crosslinker; (3) at least one filler;(4) at least one pre-structuring compound; and (5) at least one liquidinjection molding inhibitor, wherein said base feed line feeds into thebarrel of an injection molding machine; (b) feeding into said base feedline containing said liquid silicone rubber base a catalyst master batchcomprising: (1) at least one catalyst; and (2) at least one vinylsiloxane polymer; (c) transferring said liquid silicone rubber base andsaid catalyst master batch into the barrel of the injection moldingmachine via the base feed line; (d) operating said injection moldingmachine, thereby mixing said liquid silicone rubber base and saidcatalyst master batch; and (e) curing said mixed liquid silicone rubberbase and catalyst master batch by heating. In one aspect of thisembodiment, the base feed line feeds into the injection molding machinewithout any static or dynamic mixers in the line. In another aspect ofthis embodiment, the base feed line feeds into a dynamic or a staticmixer between steps (b) and (c) above.

In yet another embodiment, a method of producing a molded siliconerubber product is disclosed comprising: (a) feeding into a base feedline a liquid silicone rubber base comprising: (1) at least one vinylsiloxane polymer; (2) at least one hydride crosslinker; (3) at least onefiller; (4) at least one pre-structuring compound; (5) at least onesilicone release agent; and (6) at least one liquid injection moldinginhibitor, wherein said base feed line feeds into the barrel of aninjection molding machine; (b) feeding into said base feed linecontaining said liquid silicone rubber base a catalyst master batchcomprising: (1) at least one catalyst; and (2) at least one vinylsiloxane polymer; (c) transferring said liquid silicone rubber base andsaid catalyst master batch into the barrel of the injection moldingmachine via the base feed line; (d) operating said injection moldingmachine, thereby mixing said liquid silicone rubber base and saidcatalyst master batch; and (e) curing said mixed liquid silicone rubberbase and catalyst master batch by heating. In one aspect of thisembodiment, the base feed line feeds into the injection molding machinewithout any static or dynamic mixers in the line. In another aspect ofthis embodiment, the base feed line feeds into a dynamic or a staticmixer between steps (b) and (c) above.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer and at least one hydridecrosslinker.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, and at least one liquid injection molding inhibitor.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one liquid injection molding inhibitor, and atleast one filler.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one liquid injection molding inhibitor, at leastone filler, and at least one pre-structuring compound.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one liquid injection molding inhibitor, at leastone filler, at least one pre-structuring compound, and at least onesilicone release agent.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one filler, at least one pre-structuring compound,and at least one silicone release agent.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one filler, and at least one pre-structuringcompound.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, and at least one filler.

In an alternate embodiment, a liquid silicone rubber base is providedcomprising at least one vinyl siloxane polymer, at least one hydridecrosslinker, at least one filler, at least one pre-structuring compound,at least one release agent; and optionally, at least one injectionmolding inhibitor, but no catalyst. In one aspect of this embodiment: a)the at least one vinyl siloxane polymer is selected from the groupconsisting of: Formula I-3, Formula I-4, Formula I-5, Formula I-6, andFormula I-7, as defined below, and combinations thereof, wherein: theradical R are, independently, selected from the group consisting ofmonovalent hydrocarbon radicals and halogenated monovalent hydrocarbonradicals; the radical R¹ are, independently, selected from the groupconsisting of phenyl, lower alkenyl of 2 to 8 carbon atoms, lower alkylof 1 to 8 carbon atoms and mononuclear aryl radicals; the radical R²are, independently, selected from the group consisting of an alkylradical, a mononuclear aryl radical, a lower alkyl radical of 1 to 8carbon atoms, a phenyl radical, lower alkenyl of 2 to 8 carbon atoms,and a vinyl group; the radical R″ are, independently, selected from thesame groups as the radical R¹; Vi denotes vinyl; m is an integer fromabout 100 to about 10,000; n is an integer from about 100 to about 400;o is an integer from about 2 to about 8; p is an integer from about 100to about 200; q is an integer from about 5 to about 15; w is an integerfrom about 0 to about 500; x is an integer from about 100 to about10,000; y is an integer from about 0 to about 300; and z is an integerfrom about 0 to about 200; b) the at least one hydride crosslinker isselected from the group consisting of: Formula II-3, Formula II-4,Formula II-5, Formula II-6, and Formula II-7, as defined below, andcombinations thereof, wherein: each R⁴ is selected, independently, fromthe group consisting of hydrogen, monovalent hydrocarbon radicals, andhalogenated monovalent hydrocarbon radicals; each R⁵ radical isselected, independently, from the group consisting of monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals; sis an integer from about 1 to about 1000; t is an integer from about 5to about 200; u is an integer from about 14 to about 30; v is an integerfrom about 12 to about 21; w is an integer from about 2 to about 8; x isan integer from about 3 to about 9; y is an integer from about 5 toabout 15; M is monofunctional trimethylsilyl or (CH₃)₃SiO_(1/2); H ishydrogen; and Q is tetrafunctional silicon dioxide or SiO_(4/2); c) theat least one filler is in situ treated fumed silica treated withhexamethyldisilazane and tetramethyldivinyldisilazane; d) the at leastone pre-structuring compound has the formula: Formula X, wherein R isselected from the group consisting of monovalent hydrocarbon radicals,and halogenated monovalent hydrocarbon radicals; and n is an integerfrom about 0 to about 12, e) the at least one release agent has theformula M_(x)Q^(OH), wherein x is an integer from about 1 to about 3,and F the optional at least one liquid injection molding inhibitor ispresent at a concentration of about 0.0 parts per 100 to about 1.4 partsper 100, and is selected from the group consisting of: Formula III,Formula VI, and combinations thereof, wherein: i) R¹ has the formula ofFormula IV; ii) R² is selected from the group consisting of Formula IV,hydrogen, triorganosilyl radicals, siloxanes, and Formula V; iii) R³ isselected from the group consisting of: of divalent hydrocarbonradicalsconsisting of linear or branched alkyl radicals having from about 1 toabout 10 carbon atoms; linear or branched alkenyl radicals having fromabout 1 to about 10 carbon atoms; linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; cycloalkyl radicals havingfrom about 3 to about 12 carbon atoms; cycloalkenyl radicals having fromabout 3 to about 12 carbon atoms; cycloalkynyl radicals having fromabout 8 to about 16 carbon atoms; fluorinated linear or branched alkylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkyl radicals having from about 1 to about 10 carbonatoms; brominated linear or branched alkyl radicals having from about 1to about 10 carbon atoms; fluorinated linear or branched alkenylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkenyl radicals having from about 1 to about 10carbon atoms; brominated linear or branched alkenyl radicals having fromabout 1 to about 10 carbon atoms; fluorinated linear or branched alkynylradicals having from about 1 to about 10 carbon atoms; chlorinatedlinear or branched alkynyl radicals having from about 1 to about 10carbon atoms; brominated linear or branched alkynyl radicals having fromabout 1 to about 10 carbon atoms; hydrocarbonoxy radicals containing atleast two carbon atoms; fluorinated hydrocarbonoxy radicals containingat least two carbon atoms; chlorinated hydrocarbonoxy radicalscontaining at least two carbon atoms; brominated hydrocarbonoxy radicalscontaining at least two carbon atoms; aryl radicals; linear or branchedalkyl aryl radicals; fluorinated aryl radicals; chlorinated arylradicals; brominated aryl radicals; fluorinated linear or branchedalkyl-, alkenyl-, or alkynyl aryl radicals; chlorinated linear orbranched alkyl-, alkenyl-, or alkynyl aryl radicals; and brominatedlinear or branched alkyl-, alkenyl-, or alkynyl aryl radicals; iv) R⁴ isselected from the group of monovalent radicals consisting of: hydrogen,linear or branched alkyl radicals having from about 1 to about 10 carbonatoms; linear or branched alkenyl radicals having from about 1 to about10 carbon atoms; linear or branched alkynyl radicals having from about 1to about 10 carbon atoms; cycloalkyl radicals having from about 3 toabout 12 carbon atoms; cycloalkenyl radicals having from about 3 toabout 12 carbon atoms; cycloalkynyl radicals having from about 8 toabout 16 carbon atoms; fluorinated linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkyl radicals having from about 1 toabout 10 carbon atoms; fluorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; fluorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; chlorinated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;brominated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; hydrocarbonoxy radicals containing at least twocarbon atoms; fluorinated hydrocarbonoxy radicals containing at leasttwo carbon atoms; chlorinated hydrocarbonoxy radicals containing atleast two carbon atoms; brominated hydrocarbonoxy radicals containing atleast two carbon atoms aryl radicals; linear or branched alkyl arylradicals; fluorinated aryl radicals; chlorinated aryl radicals;brominated aryl radicals; fluorinated linear or branched alkyl-,alkenyl-, or alkynyl aryl radicals; chlorinated linear or branchedalkyl-, alkenyl-, or alkynyl aryl radicals; brominated linear orbranched alkyl-, alkenyl-, or alkynyl aryl radicals; and triorganosilylradicals; and v) R is selected from the group consisting of: hydrogen;alkyl; phenyl; and C_(x)H_(y), where x is an integer from about 2 toabout 10, and y is an integer from about 4 to about 21. Preferably, atleast three R⁴ groups of Formula II—3—if used at b), above—are hydrogen.

In an alternate embodiment, a catalyst master batch is providedcomprising at least one catalyst and at least one vinyl siloxanepolymer.

In an alternate embodiment, an inhibitor master batch is providedcomprising at least one liquid injection molding inhibitor and at leastone vinyl siloxane polymer.

In an alternate embodiment, a molded silicone rubber article isprovided, produced by using a liquid silicone rubber base comprising: atleast one vinyl siloxane polymer; at least one hydride crosslinker; atleast one filler; at least one pre-structuring compound; at least onerelease agent; and optionally, at least one injection molding inhibitor;but no catalyst.

Other processes and products in accordance with the process are providedin the detailed description and claims that follow below. Additionalobjects, features, and advantages will be sent forth in the descriptionthat follows, and in part, will be obvious from the description, or maybe learned by practice of the invention. The objects, features, andadvantages may be realized and obtained by means of theinstrumentalities and combination particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature, objects, and advantages ofthe present invention, reference should be had to the following detaileddescription, read in conjunction with the following drawings, whereinlike reference numerals denote like elements.

FIG. 1 is a schematic representation of a standard two-part liquidsilicone rubber process of the prior art, for producing a moldedsilicone rubber product, wherein components A and B are mixed in astatic or dynamic mixer before being introduced into the injectionmolding machine.

FIG. 2 is a schematic representation of an example of a method forproducing a molded silicone rubber product, wherein the inhibitor andcatalyst master batches are separate from the liquid silicone rubberbase, and the inhibitor and catalyst streams are fed into the base feedline prior to their introduction into the barrel of the injectionmolding machine.

FIG. 3 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 2, wherein the base feed line enters a mixer at a point after—orbelow the point at which—inhibitor master batch enters the base feedline and before—or above the point at which—catalyst master batch entersthe base feed line.

FIG. 4 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 3, wherein the base feed line enters a mixer at a point after—orbelow the point at which—catalyst master batch enters the base feedline.

FIG. 5 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIGS. 3 and 4, wherein the base feed line feeds into a first mixerafter—or below the point at which—inhibitor master batch enters the basefeed line and before—or above the point at which—catalyst master batchenters the base feed line. Subsequently, the base feed line feeds into asecond mixer after—or below the point at which—catalyst master batchenters the base feed line.

FIG. 6 is a schematic representation of an example of a method forproducing a molded silicone rubber product, wherein the liquid siliconerubber base contains at least one injection molding inhibitor, and thebase is separate from the catalyst master batch. The liquid siliconerubber base and catalyst master batch are fed separately into the basefeed line, which then feeds into the injection molding machine barrel ata single entry point.

FIG. 7 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 6, wherein the base feed line enters a mixer at a point after—orbelow the point at which—catalyst master batch enters the base feedline.

FIG. 8 is a schematic representation of an example of a method of thepresent invention for producing a molded silicone rubber product.

FIG. 9 is a schematic representation of an example of a method of thepresent invention for producing a molded silicone rubber product wherethe inhibitor is removed from the base.

FIG. 10 is a schematic representation of an example of a method forproducing a molded silicone rubber product where the inhibitor isremoved from the base and there is a separate feed for part of the vinylsiloxane polymers.

FIG. 11 is a schematic representation of an example of a method forproducing a molded silicone rubber product where the inhibitor isremoved from the base and the separate vinyl siloxane polymer feed isfed into the inhibitor stream prior to introduction into the mixer.

FIG. 12 is a schematic representation of an example of a method forproducing a molded silicone rubber product, wherein the inhibitor,additive, and catalyst master batches are separate from the liquidsilicone rubber base, and the inhibitor, additive, and catalyst streamsare fed into the base feed line prior to their introduction into thebarrel of the injection molding machine.

FIG. 13 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 12, wherein the base feed line enters a mixer at a point after—orbelow the point at which—inhibitor master batch, additive master batch,and catalyst master batch enter the base feed line.

FIG. 14 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 13, wherein the base feed line enters a mixer at a point after—orbelow the point at which—inhibitor master batch and additive masterbatch enter the base feed line and before—or above the point atwhich—catalyst master batch enters the base feed line, and wherein thebase feed line enters a second mixer at a point after—or below the pointat which—catalyst master batch enters the base feed line.

FIG. 15 is a schematic representation of an example of a method forproducing a molded silicone rubber product, similar to that shown inFIG. 14, wherein the base feed line enters a mixer at a point after—orbelow the point at which—inhibitor master batch enters the base feedline and before—or above the point at which—additive master batch andcatalyst master batch enter the base feed line, wherein the base feedline enters a second mixer at a point after—or below the point atwhich—additive master batch enters the base feed line and before—orabove the point at which—catalyst master batch enters the base feedline, and wherein the base feed line enters a third mixer at a pointafter—or below the point at which—catalyst master batch enters the basefeed line.

DETAILED DESCRIPTION OF THE INVENTION

Before the subject invention is further described, it is to beunderstood that the invention is not limited to the particularembodiments of the invention described below, as variations of theparticular embodiments may be made and still fall within the scope ofthe appended claims. It is also to be understood that the terminologyemployed is for the purpose of describing particular embodiments, and isnot intended to be limiting. Instead, the scope of the present inventionwill be established by the appended claims.

In this specification and the appended claims, the singular forms “a,”“an,” and “the” include plural reference unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood to one of ordinary skill in the art to which this inventionbelongs.

Disclosed is a novel process for the preparation of molded siliconerubber products.

Generally, the process uses a single LSR base comprising at least onevinyl siloxane polymer, at least one silicone hydride cross linker, and(optionally) at least one liquid injection molding inhibitor. Otheroptional base components may include additional vinyl siloxane polymers,fillers, releasing agents, pre-structuring compounds, and additionalsilicone hydride crosslinkers. Separate from the base is a mixture of atleast one catalyst and at least one vinyl siloxane polymers (thecatalyst master batch), and a mixture of at least one inhibitor and atleast one vinyl siloxane polymer (the inhibitor master batch). Onebenefit afforded by a separate inhibitor master batch is improvedcontrol over the curing time when dealing with different size injectionmolded parts. Optionally, a portion of the vinyl siloxane polymers maybe removed from the base and separately added (e.g., added to theinhibitor as a component of the inhibitor master batch or as a componentof the catalyst master batch). This provides even greater control overthe curing time and cured part physical properties. The single LSR basemay optionally comprise a trace amount of at least one injection moldinginhibitor, or about 0.0125 parts per 100 in the LSR base.

The single LSR base can be fed into a liquid injection molding machine,along with the catalyst master batch (catalyst/vinyl siloxane mixture).Components not present in the base (e.g., the catalyst and theinhibitor) can be added separately to the liquid injection moldingmachine (e.g., directly into the barrel) or injected into the base feedline (e.g., the line containing the LSR base, and connecting the sourceof LSR base to the injection molding machine). The single LSR base maycomprise at least one vinyl siloxane polymer, at least one siliconehydride cross linker, and (optionally) at least one liquid injectionmolding inhibitor. In one embodiment, the at least one vinyl siloxanepolymer comprises at least one polyorganosiloxane (I) containing, permolecule, at least two C₂-C₆ alkenyl groups linked to silicon. Thepolyorganosiloxane (I) is one of the essential constituents of thesingle LSR base.

Advantageously, it is a product comprising:

(i) siloxyl units of formula:

$\begin{matrix}{R_{a}^{1}z_{b}{{Si}O}\frac{4 - \left( {a + b} \right)}{2}} & {{Formula}\mspace{14mu} I\text{-}1}\end{matrix}$

in which:

-   -   (a) the symbols R¹ represent an alkenyl group, preferably vinyl        or allyl,    -   (b) the symbols Z, which may be identical or different, each        represent a monovalent hydrocarbon-based group, free of        unfavourable action on the activity of the catalyst and chosen        from alkyl groups containing from 1 to 8 carbon atoms inclusive,        optionally substituted with at least one halogen atom, and also        from aryl groups,    -   (c) a is 1 or 2, b is 0, 1 or 2 and the sum a+b is equal to 1, 2        or 3, and optionally

(ii) other siloxyl units of formula:

Z_(c)SiO_(4/2)  Formula I-2

in which Z has the same meaning as above and c is 0, 1, 2 or 3.

The polyorganosiloxane (I) may be formed solely from units of FormulaI-1 or may contain, in addition, units of Formula I-2. Similarly, it mayhave a linear or branched structure. Z is generally chosen from methyl,ethyl and phenyl radicals, 60 mol % (or in numerical terms) at least ofthe radicals Z being methyl radicals. Examples of siloxyl units offormula (I-1) are vinyldimethylsiloxyl, vinylphenylmethylsiloxyl,vinylmethylsiloxyl and vinylsiloxyl units.

Examples of siloxyl units of Formula I-2 are the units SiO_(4/2),dimethylsiloxyl, methylphenylsiloxyl, diphenylsiloxyl, methylsiloxyl andphenylsiloxyl. Examples of polyorganosiloxanes (I) are for instance:dimethylpolysiloxanes containing dimethylvinylsilyl end groups,(methylvinyl)(dimethyl)polysiloxane copolymers containing trimethylsilylend groups and (methylvinyl)(dimethyl)polysiloxane copolymers containingdimethylvinylsilyl end groups.

Other examples of polyorganosiloxanes (I) may include the following:

where Vi stands for vinyl in Formula I-3.

The radical R in Formulas I-3 and I-4 is selected from monovalenthydrocarbon radicals and halogenated monovalent hydrocarbon radicals,that is, radicals normally associates as substituent groups for siliconepolysiloxanes. Thus, the radical R in the vinyl containing polysiloxanesof Formula I-3 and I-4 may be individually selected from the classconsisting of mononuclear and binuclear aryl radicals such as, phenyl,tolyl, xylyl, napthyl; halogenated mononuclear and binuclear arylradicals such as, chlorophenyl, chloronaphtyl; mononuclear aryl loweralkyl radicals having from 1 to 8 carbon atoms per alkyl group such asbenzyl, phenyl; lower alkyl radicals having from 1 to 8 carbon atomssuch as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl; loweralkenyl radicals having from 2 to 8 carbon atoms such as, vinyl, allyl,and 1-propenyl; halo lower alkyl radicals having from 1 to 8 carbonatoms such as chloropropyl, trifluoropropyl, and cycloalkyl radicalssuch as, cyclobutyl, cyclopentyl, and cyclohexyl. Preferably, the Rradical in the vinyl containing polysiloxanes of Formula I-3 and I-4 isa lower alkyl radical of 1 to 8 carbon atoms such as methyl, ethyl, andphenyl. The R radicals in Formula I-3 and I-4 can be the same ordifferent.

The radical R¹ in Formula I-3 and I-4 is selected from the classconsisting of lower alkenyl of 2 to 8 carbon atoms, lower alkyl of 1 to8 carbon atoms and mononuclear aryl radicals. R¹ can also be a phenyl.Preferably, the radical R¹ in Formula I-3 and I-4 is methyl. The R¹radicals in Formula I-3 and I-4 can be the same or different.

The radical R² in Formula I-3 and I-4 is preferably an alkyl radical ora mononuclear aryl radical and is more preferably a lower alkyl radicalof 1 to 8 carbon atoms or a phenyl radical or from the class consistingof lower alkenyl of 2 to 8 carbon atoms. The R² radical can also be avinyl group. The two R² radicals can be the same or different.

The R″ radical in Formula I-4 is selected from the same groups as the R¹radical, that is, groups selected from the class consisting of alkyl,aryl, and alkenyl radicals and the R″ radical is preferably selectedfrom the class consisting of lower alkyl radicals of 1 to 8 carbonatoms, phenyl radicals and lower alkenyl radicals of 2 to 8 carbonatoms. Most preferably, the R″ radical is selected from methyl, ethyl,propyl, vinyl, and allyl. The R″ radicals can be the same or different.

Formula I-3 vinyl siloxane polymers may have a viscosity of from about5000 centipoise to about 1,000,000 centipoise at 25° C. In Formula I-3vinyl siloxane polymers, x varies from about 100 to about 10,000 and yvaries from about 0 to about 300. More preferably, x varies from about500 to about 2000 and y varies from about 0 to about 300.

Formula I-4 vinyl siloxane polymers may have a viscosity of from about50 centipoise to about 5,000 centipoise, and more preferably from about50 centipoise to about 2,000 centipoise at 25° C. In Formula I-4, wgenerally varies from about 0 to about 500 and z varies from about 0 toabout 200. More preferably, w varies from about 50 to about 300 and zvaries from about 0 to about 100.

Preferably, the vinyl siloxane polymers are 5,000 to 1,000,000centipoise dimethylvinyl terminated polydimethlysiloxane polymer ofFormula I-5; 500 to 100,000 centipoise trimethyl terminated methylvinyldimethylsiloxane copolymer of Formula I-6; and 100 to 100,000 centipoisedimethylvinyl terminated methylvinyl, dimethylsiloxane copolymer ofFormula I-7. More preferably, the vinyl siloxane polymers are 40,000 to100,000 centipoise dimethylvinyl terminated polydimethylsiloxane polymerof Formula I-5; about 1000 centipoise trimethyl terminated, methylvinyldimethylsiloxane copolymer of Formula I-6; and about 400 centipoisedimethylvinyl terminated methylvinyl dimethylsiloxane copolymer ofFormula I-7, as shown below:

where Vi stands for vinyl, and m varies from about 100 to 10,000 andpreferably 500 to 2000; n varies from about 100 to 400, and preferably220 to 280 o varies from about 2.0 to 8.0, and preferably 3.0 to 5.0; pvaries from about 100 to 200, and preferably 130 to 155; and q variesfrom about 5.0 to 15.0, and preferably 8.0 to 12.0.

The at least one silicone hydride cross linker may includehydrogen-containing silanes, hydrogen-containing siloxanes,hydrogen-containing polysiloxanes, and mixtures thereof. In oneembodiment, the silicone hydride crosslinkers may be a polysiloxaneresin having the formula H(R³)₂SiO_(1/2) units and SiO₂ units where theratio of the monofunctional units to tetrafunctional units may vary from0.5:1 to 10:1, and is preferably about 2:1. The hydroxyl and alkoxycontent of such a resin is preferably less than 0.5 weight percent basedon the weight of the resin. The R³ radical is selected from the classconsisting of hydrogen, monovalent hydrocarbon radicals, and halogenatedmonovalent hydrocarbon radicals. Thus, the radical R³ may be selectedfrom the same radicals as discussed above with respect to the R radicalappearing in Formulas I-3 and I-4. Preferably, the R³ radical is a loweralkyl radical of 1 to 8 carbons such as, methyl and ethyl.

In another embodiment, when the at least one silicone hydride crosslinker is chosen from a hydrogen containing polysiloxanes (II) it maycomprise siloxyl units of formula:

$\begin{matrix}{H_{d}L_{e}{SiO}\frac{4 - \left( {d + e} \right)}{2}} & {{Formula}\mspace{14mu} {II}\text{-}1}\end{matrix}$

in which:

-   -   (i) the groups L, which may be identical or different, each        represent a monovalent hydrocarbon-based group, free of        unfavourable action on the activity of the catalyst and chosen,        preferably, from an alkyl group containing from 1 to 8 carbon        atoms inclusive, optionally substituted with at least one        halogen atom, advantageously from methyl, ethyl, propyl and        3,3,3-trifluoropropyl groups, an aryl group, and advantageously        a xylyl, tolyl or phenyl radical;    -   (ii) d is 1 or 2, e is 0, 1 or 2, the sum d+e is equal to 1, 2        or 3; and    -   (iii) optionally, at least some of the other units being units        of mean formula:

$\begin{matrix}{L_{g}{SiO}\frac{4 - g}{2}} & {{Formula}\mspace{14mu} {II}\text{-}2}\end{matrix}$

in which the groups L have the same meaning as above and g is equal to0, 1, 2 or 3.

The polyorganosiloxane (II) may be formed solely from units of formulaII-1) or may also comprise units of Formula II-2. The polyorganosiloxane(II) may have a linear or branched, structure. The group L has the samemeaning as the group Z above.

Examples of units of Formula II-1 are H(CH₃)₂SiO_(1/2), HCH₃SiO_(2/2)and H(C₆H₅)SiO_(2/2).

The examples of units of Formula II-2 are the same as those given abovefor the units of Formula I-2.

Examples of polyorganosiloxanes (II) are for instance:

-   -   (i) dimethylpolysiloxanes containing hydrogenodimethylsilyl end        groups;    -   (ii) copolymers containing        (dimethyl)(hydrogenomethyl)polysiloxane units containing        trimethylsilyl end groups;    -   (iii) copolymers containing        (dimethyl)(hydrogenomethyl)polysiloxane units containing        hydrogenodimethylsilyl end groups; and    -   (iv) hydrogenomethylpolysiloxanes containing trimethylsilyl end        groups.

In an alternate embodiment the at least one silicone hydride crosslinker may have the following formula:

wherein each R⁴ is selected, independently, from the class consisting ofhydrogen, monovalent hydrocarbon radicals and halogenated monovalenthydrocarbon radicals, or the same radicals as the R radicals that weredefined above with respect to the vinyl polysiloxanes of Formulas I-3and I-4. Preferably, at least three R⁴ groups of Formula II-3 arehydrogen. Each R⁵ radical is selected, independently, from the classconsisting of monovalent hydrocarbon radicals, halogenated monovalenthydrocarbon radicals, or the same radicals that were defined withrespect to the R radical in connection with the definition of thecompounds of Formulas I-3 and I-4. The R⁴ radicals can be the same ordifferent. The R⁵ radicals can be the same or different. In FormulaII-3, s varies between about 1 to about 1000 and t varies from about 5to about 200. More preferably, s varies from about 10 to about 100, andt varies from about 5 to about 200.

In other preferred embodiments, the at least one silicone hydridecrosslinker may have the following formulas:

Another type of hydride polymer used to extend the polysiloxane chainlength for the purpose of increasing elongation and decreasing modulushas the following formula:

In Formula II-4, u ranges from about 14 to about 30, preferably 19 to23, most preferred c is 21; and v ranges from about 12 to about 21,preferably 15 to 18, most preferred 16.

In Formula II-5, w ranges from about 2 to about 8, preferably 3 to 6,most preferred c is 5; and x ranges from about 3 to about 9, preferably5 to 7, most preferred 6.

In Formula II-6, y ranges from about 5 to about 15, preferably 7 to 10,most preferred 8.

In another preferred embodiment, the at least one silicone hydridecrosslinker may have the following formula:

M₂ ^(H)Q  Formula II-7

which is a dimethyl hydrogen stopped Q hydride cross linker, where M andQ refer to the nomenclature explained in the research monograph by H. A.Liebhafsky, “Silicones Under the Monogram,” published byWiley—Interscience division of John Wiley and Sons, New York(publication date 1978) at pages 99 and following, and which is herebyincorporated by reference in its entirety. In brief, M is monofunctionaltrimethylsilyl or (CH₃)₃SiO_(1/2); H is hydrogen, and Q istetrafunctional silicon dioxide or SiO_(4/2).

The preparation of the polysiloxanes of Formulas I-1-I-7 is well knownin the art. U.S. Pat. No. 2,406,621, which is hereby incorporated byreference in its entirety, describes a general method for preparingpolysiloxanes. The hydrogen containing siloxane resin containingmonofunction units and tetrafunctional units may be produced by methodswell known in the art, such as U.S. Pat. No. 2,857,356, which is herebyincorporated by reference in its entirety. The hydride cross linkers ofFormulas II-1-II-7 may be produced by methods well known in the art,such as, U.S. Pat. Nos. 3,697,473 and 3,989,688, which are herebyincorporated by reference in their entirety.

The at least one injection molding inhibitor can be any compound thatslows down the curing time of an LSR process. Preferably, the inhibitorsare selected from the class consisting of acetylenic alcohols asdescribed in U.S. Pat. No. 3,445,420, which is hereby incorporated byreference in its entirety. Further, the at least one injection moldinginhibitor may also have the formula:

wherein R¹ has the formula:

—R³—C≡C—R⁴  Formula IV

wherein R³ is selected from the group of divalent hydrocarbonradicalsconsisting of linear or branched alkyl radicals having from 1 to about10 carbon atoms, linear or branched alkenyl radicals having from 1 toabout 10 carbon atoms, linear or branched alkynyl radicals having from 1to about 10 carbon atoms, cycloalkyl radicals having from 3 to about 12carbon atoms, cyclo alkenyl radicals having from about 3 to 12 carbonatoms, cyclo alkynyl radicals having from about 5 to about 16 carbonatoms, fluorinated linear or branched alkyl radicals having from 1 toabout 10 carbon atoms, chlorinated linear or branched alkyl radicalshaving from 1 to about 10 carbon atoms, brominated linear or branchedalkyl radicals having from 1 to about 10 carbon atoms, fluorinatedlinear or branched alkenyl radicals having from 1 to about 10 carbonatoms, chlorinated linear or branched alkenyl radicals having from 1 toabout 10 carbon atoms, brominated linear or branched alkenyl radicalshaving from 1 to about 10 carbon atoms, fluorinated linear or branchedalkynyl radicals having from 1 to about 10 carbon atoms, chlorinatedlinear or branched alkynyl radicals having from 1 to about 10 carbonatoms, brominated linear or branched alkynyl radicals having from 1 toabout 10 carbon atoms, hydrocarbonoxy radicals containing at least tocarbon atoms, fluorinated hydrocarbonoxy radicals containing at least tocarbon atoms, chlorinated hydrocarbonoxy radicals containing at least tocarbon atoms, brominated hydrocarbonoxy radicals containing at least tocarbon atoms, aryl radicals, linear or branched alkyl aryl radicals,fluorinated aryl radicals, chlorinated aryl radicals, brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; and brominated linear or branched alkyl-,alkenyl-, or alkynyl aryl radicals; and wherein R⁴ is selected from thegroup of monovalent radicals consisting of hydrogen, linear or branchedalkyl radicals having from 1 to about 10 carbon atoms, linear orbranched alkenyl radicals having from 1 to about 10 carbon atoms, linearor branched alkynyl radicals having from 1 to about 10 carbon atoms,cycloalkyl radicals having from 3 to about 12 carbon atoms, cycloalkenylradicals having from about 3 to 12 carbon atoms, cycloalkynyl radicalshaving from about 8 to about 16 carbon atoms, fluorinated linear orbranched alkyl radicals having from 1 to about 10 carbon atoms,chlorinated linear or branched alkyl radicals having from 1 to about 10carbon atoms, brominated linear or branched alkyl radicals having from 1to about 10 carbon atoms, fluorinated linear or branched alkenylradicals having from 1 to about 10 carbon atoms, chlorinated linear orbranched alkenyl radicals having from 1 to about 10 carbon atoms,brominated linear or branched alkenyl radicals having from 1 to about 10carbon atoms, fluorinated linear or branched alkynyl radicals havingfrom 1 to about 10 carbon atoms, chlorinated linear or branched alkynylradicals having from 1 to about 10 carbon atoms, brominated linear orbranched alkynyl radicals having from 1 to about 10 carbon atoms,hydrocarbonoxy radicals containing at least two carbon atoms,fluorinated hydrocarbonoxy radicals containing at least two carbonatoms, chlorinated hydrocarbonoxy radicals containing at least twocarbon atoms, brominated hydrocarbonoxy radicals containing at least twocarbon atoms aryl radicals, linear or branched alkyl aryl radicals,fluorinated aryl radicals, chlorinated aryl radicals, brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; brominated linear or branched alkyl-, alkenyl-,or alkynyl aryl radicals; and triorganosilyl radicals and wherein R² maybe R¹ or selected from the group consisting of hydrogen, triorganosilylradicals, and siloxanes wherein the structural geometry of the compoundaround the double bond may be either cis or trans.

More preferably, the at least one injection molding inhibitor has thefollowing formula:

where R may be hydrogen, alkyl, or a phenyl. R may also have thefollowing formula: C_(x)H_(y), where x ranges from about 2 to about 10,and y ranges from about 4 to about 21.

Most preferably, the at least one injection molding inhibitor is anethynyl cyclohexanol of the following formula:

The at least one catalyst can be any transition metal containingcompound that facilitates a reaction between the vinyl functional groupon the vinyl polysiloxane polymers and the hydrogen functional group onthe hydride cross linkers. Typical transition metal catalysts areplatinum, rhodium, ruthenium, palladium, and iridium. Preferably, the atleast one catalyst is a platinum complex (a “platinum catalyst” or“platinum compound”). When optical clarity in the finished molded partis required, the platinum compound can be selected from those having theformula (PtCl₂Olefin)₂ and H(PtCl₃Olefin) as described in U.S. Pat. No.3,159,601, which is hereby incorporated by reference in its entirety.The olefin in the previous two formulas can be almost any type of olefinbut is preferably an alkenylene having from 2 to 8 carbon atoms, acycloalkenylene having from 5 to 7 carbon atoms or styrene. Specificolefins utilizable in the above formulas are ethylene, propylene, thevarious isomers of butylene, octylene, cyclopentene, cyclohexene, andcycloheptene.

In another embodiment, the platinum-containing material is platinumchloride cyclopropane complex (PtCl₂C₃H₆) described in U.S. Pat. No.3,159,662, which is hereby incorporated by reference in its entirety.

In yet a further embodiment, the platinum containing material can be acomplex formed from chloroplatinic acid with up to 2 moles per gram ofplatinum of a member selected from the class consisting of alcohols,ethers, aldehydes and mixtures of the above as described in U.S. Pat.No. 3,220,972, which is hereby incorporated by reference in itsentirety.

In yet another embodiment, the platinum catalyst is a platinummethylvinyl complex as described in U.S. Pat. Nos. 3,715,334; 3,775,452;and 3,814,730, each of which are hereby incorporated by reference intheir entirety, formed via a reaction between H₂PtCl₆+6H₂O+ dimethylvinyl terminated polydimethlysiloxane polymer. Preferably, the platinumcompound catalyst, which contains about 10% platinum, is diluted toabout 11% to about 0.1% platinum methylvinyl complex in about 99% toabout 99.9% dimethylvinyl terminated polydimethlysiloxane polymer.

Optional LSR base components may include at least one filler, at leastone releasing agent, and at least one pre-structuring compound. Fillersare used to obtain high tensile strength molded products. Examples offillers include: titanium dioxide, lithopone, zinc oxide, zirconiumsilicate, silica aerogel, iron oxide, diatomaceous earth, calciumcarbonate, fumed silica, silazane treated silica, precipitated silica,organosiloxane and cyclic organosiloxane treated silica, glass fibers,magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, alphaquartz, carbon black, calcined clay, asbestos, carbon, graphite, cork,cotton, and synthetic fibers.

The preferred fillers may be either fumed silica or a precipitatedsilica that may have been surfaced treated. In one method of surfacetreatment, the fumed silica or precipitated silica is exposed to cyclicorganopolysiloxanes under heat and pressure. An additional method oftreating fillers is one in which the silica is exposed to siloxanes orsilanes in the presence of an amine compound.

Another method of surface treating silica fillers employs methyl silaneor silazane surface treating agents. Methylsilane or silazane surfacetreated fumed or precipitated silica fillers exhibit the property ofproducing pumpable silicone compounds and also do not overly increasethe low viscosity of the uncured liquid precursor silicone composition.After curing, silazane treated silicas impart an improved tear strengthto the cured elastomer. U.S. Pat. Nos. 3,365,743 and 3,847,848 disclosesuch methods, and are hereby incorporated by reference in theirentirety.

More preferred silica fillers are in situ formed fumed silica with asurface area between about 100 m² per gram to about 600 m² per gram, andmost preferably between about 200 m² per gram to about 400 m² per gram.In situ treated fumed silica occurs when the silanols on the surface ofthe fumed silica are capped with a silicon atom containing alkyl, aryl,or alkenyl pendant groups while being compounded with the polymer in themixer. This process can utilize hexamethyldisilazane,tetramethyldivinyldisilazane or a suitable silanol capping agent knownin the art, such as trimethylsilanol and dimethylvinylsilanol to treatthe filler.

The fumed silica can have a surface with silicon atoms to which arebonded organosiloxane groups and hydroxide groups. The organosiloxanegroups bonded to the silica surface may be

where x ranges from about 0 to about 20 and y ranges from about 1 toabout 10. The organosiloxane groups are present on the silica in anamount sufficient to provide from about 0.05 to about 0.32 percent byweight vinyl radical bases on the weight of the silica, and are presentin a mole ratio such that there is from about 7 to about 50 moles oforganosiloxane group from Formula VII(a) for each mole of organosiloxanegroup from Formula VII(b), VII(c), VII(d), VII(e), or mixtures thereof.

Preferably, the organosiloxane groups on the silica are a combination ofFormula VII(a), VII(b), and hydroxide groups which x is about 0 to about5, or a combination of Formula VII(a), VII(d), and hydroxide groups. Themole ratio of trimethylsiloxy groups to dimethylvinylsiloxy groups isabout 50:1 to about 5:1. The methods of treating silica in situ are wellknown in the art. The treating compounds can includehexamethyldisilazane for Formula VII(a) organosiloxane groups,symmetrical-tetramethyldivinyldisilazane, hexamethyldisilazane havingthe formula:

(CH₃)₃Si—NH—Si(CH₃)₃  Formula VIII(a)

and tetramethyldivinyldisilazane having the formula

CH₂═CH(CH₃)₂Si—NH—Si(CH₃)₂CH═CH₂  Formula VIII(b)

for Formula VII(b); organosiloxane groups,symmetrical-dimethyldiphenyldivinyldisilazane for Formula VII(c);organosiloxane groups and hydroxyl enblocked polydiorganosiloxane havingabout 1 to about 5 methylvinylsiloxane units and about 1 to about 10dimethylsiloxane units for Formula VII(d); organosiloxane groups, andhydroxyl enblocked polyorganosiloxane having about 1 to about 10dimethylsiloxane units for Formula VII(e).

Other treatments to the silica filler can include cyclic polysiloxanesas described, for example, in U.S. Pat. No. 2,938,009, herebyincorporated by reference in its entirety. Another method for treatingfillers is disclosed in U.S. Pat. No. 3,024,126, hereby incorporated byreference in its entirety. The fillers may also be silazane treatedfillers in accordance with U.S. Pat. No. 3,635,743, hereby incorporatedby reference in its entirety. These fillers are generally utilized in aconcentration of 5 to 70 parts of treated filler for each 100 parts ofvinyl siloxane polymer. More preferably, the filler is utilized at aconcentration of 10 to 40 parts of filler per 100 parts of vinylsiloxane polymer.

The silicas of Formula VII can be prepared by treating silica withorganosolixane compounds and thereafter mixing the treated silica withthe other ingredients of the silicas of Formula VII can be prepared inthe presence of triorganosiloxy endblocked polydimethylsiloxane fluid,an in situ method. Such methods of treating silica are broadly known inthe art, and are applicable to this invention to prepare the treatedsilicas. Additional methods and treatments for silica fillers aredisclosed in U.S. Pat. Nos. 3,884,866; 4,162,243; and 5,928,564, andZumbrum, Adhesion International 1993, Proceedings of the 16^(th) AnnualMeeting, pp. 471-486, each of which are hereby incorporated by referencein their entirety.

Hydroxy containing organopolysiloxane fluid or resin may be added toimprove the mold release properties and extend the shelf life of theliquid injection molding organopolysiloxane composition. Where silazanetreated precipitated silica filler or fumed silica filler is present inthe composition, the hydroxyl containing organopolysiloxane fluid orresin may be added in conjunction with the precipitated silica filler orfumed silica filler to obtain extended shelf life and mold release. Thehydroxyl containing organosiloxane fluids have a viscosity of from about5 to about 100 centipoise at 25° C. and preferably from about 20 toabout 50 centipoise. These fluids or resins may be represented by theformula:

R_(q)(OH)_(r)SiO_((4-q-r)/2)  Formula IX

where R is defined as above, q may range from about 0 to about 3,preferably from about 0.5 to about 2.0, r ranges from about 0.005 toabout 2, and the sum of q and r ranges from about 0.8 to about 3.0. Thehydroxyl substitution on the organopolysiloxane fluid or resin isprimarily a terminal hydroxyl substitution. Suitable hydroxyl containingorganopolysiloxane resins have a viscosity of from about 100 to about15,000 centipoise at 25° C., and preferably from about 100 to about1,000 centipoise.

More preferably, the release agents have the formula: M_(x)Q^(OH), wherex ranges from 1 to 3, and M and Q refer to the nomenclature explained inthe research monograph by H. A. Liebhafsky, “Silicones Under theMonogram,” published by Wiley—Interscience division of John Wiley andSons, New York (publication date 1978) at pages 99 and following, andwhich is hereby incorporated by reference in its entirety. M_(x)Q^(OH)is a three-dimensional resin network that may act as a silicone releaseagent. Methods of manufacturing and the composition of the M_(x)Q^(OH)release agent can be found in U.S. Pat. Nos. 4,160,858 and 4,239,877,each of which are hereby incorporated by reference in their entirety.

The at least one pre-structuring compound can be a hydroxyorganosiloxane fluid of the following formula:

where R is defined as above and n ranges from about 0 to about 10.Preferably, the pre-structuring compound is a dimethyl silanol stoppedpolydimethylsiloxane polymer of Formula X, where R are methyl groups andn ranges from about 4 to about 10. The pre-structuring compound canreact with untreated silanols on the treated filler surface causingthickening of the compound during the compound operation and thuspreventing slow compound structuring during room temperature storage ofthe product over many years.

In one embodiment the ratio of base components can vary depending on thedesired properties of the final cured product. With respect to vinylsiloxane polymers, the base can contain either all Formula I-1, FormulaI-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, or Formula I-7,or a combination of any or all of Formulas I-1-I-7. If there is a blendof Formula I-3 and I-4, there is preferably about 20 to about 90 partsby weight, and more preferably from about 30 to about 80 parts by weightof Formula I-3; and from about 5 to about 40 parts by weight, and morepreferably from about 10 to about 30 parts by weight of Formula I-4.Such a mixture may result in the cured product having good tensilestrength, elongation, and tear strength properties.

With respect to the hydride cross linkers of Formulas II-1-II-3 and thehydrogen containing siloxane resin containing monofunctional units andtetrafunctional units, the base can contain either all Formula II-3 orall of the hydrogen containing siloxane resin, or a blend. Preferably,the hydride cross linkers are present in about 1 to about 100 parts byweight per 100 parts of vinyl siloxane polymers. More preferably, about1 to about 50 parts by weight of the hydrogen cross linkers per 100parts of vinyl siloxane polymers.

The concentration of catalyst can vary between about 0.1 parts permillion to about 50 parts per million based on the total weight of thevinyl siloxane polymer and the hydride crosslinker. Preferably, theconcentration is between about 0.1 parts per million to about 10 partsper million. The concentration of inhibitor can range between about 0parts by weight of base to about 3.0 parts by weight of base, andpreferably about 0 parts by weight of base to about 1.0 parts by weightof base. Optionally, the filler may be present in an amount betweenabout 10 parts by weight of base to about 40 parts by weight of base,and preferably between about 18 parts by weight of base to about 30parts by weight of base. Further, the release agent may be present in anamount between about 0 parts by weight of base to about 5 parts byweight of base, and preferably between about 0.2 parts by weight of baseto about 1.0 parts by weight of base. Also optional is thepre-structuring compound. This may be present in an amount from about 0parts by weight of base to about 6 parts by weight of base, andpreferably between about 0.2 parts by weight of base to about 1.0 partsby weight of base.

In another embodiment, the base can contain either separately or as ablend, vinyl siloxane polymers of Formula I-5-I-7, hydride cross linkersof Formula II-3-II-7, and an inhibitor. Optionally, the base can containfillers, releasing agents, and pre-structuring compounds. Preferably,the base can contain either Formula I-5-I-7 alone or as a blend in aconcentration between about 20 to 90 parts by weight of base, and morepreferably about 30 to 80 parts by weight of base. Regarding the hydridecross linkers of Formula II-3-II-7, they are preferably present alone oras a blend in about 1 to about 100 parts by weight per 100 parts ofvinyl siloxane polymers, and more preferably about 1 to about 50 partsby weight per 100 parts of vinyl siloxane polymers. The concentration ofcatalyst can vary between about 0.1 parts per million to about 50 partsper million based on the total weight of the vinyl siloxane polymer andthe hydride crosslinker. Preferably, the concentration is between about0.1 parts per million to about 10 parts per million. The concentrationof inhibitor can range between about 0 parts by weight of base to about2.5 parts by weight of base, and preferably about 0 parts by weigh ofbase to about 1.0 parts by weight of base. Optionally, the filler may bepresent in an amount between about 10 parts by weight of base to about40 parts by weight of base, and preferably between about 18 parts byweight of base to about 30 parts by weight of base. Further, the releaseagent may be present in an amount between about 0 parts by weight ofbase to about 5 parts by weight of base, and preferably between about0.2 parts by weight of base to about 1.0 parts by weight of base. Alsooptional is the pre-structuring compound. This may be present in anamount from about 0 parts by weight of base to about 6 parts by weightof base, and preferably between about 0.2 parts by weight of base toabout 1.0 parts by weight of base.

In an alternate embodiment, the base may contain the followingformulation—Formulation 1:

-   -   a) Formula I-5 at a viscosity of about 40,000 to about 100,000        centipoise and at a concentration of about 15 to about 90 parts        by weight of base. Preferably, the concentration is about 50 to        about 84 parts by weight of base, and most preferably about 60        to about 68 parts by weight of base.    -   b) Formula I-6 at a viscosity of about 1000 centipoise and at a        concentration of about 0 to about 10 parts by weight of base.        Preferably, the concentration is about 2 to 6 parts by weight of        base, and most preferably about 3 to about 5 parts by weight of        base.    -   c) Formula I-7 at a viscosity of about 400 centipoise and a        concentration of about 0 to about 12 parts by weight of base.        Preferably, the concentration is about 2.5 to about 8.0 parts by        weight of base, and most preferably about 3 to about 6 parts by        weight of base.    -   d) Formula II-7 at a concentration of about 0 to about 5 parts        by weight of base. Preferably, the concentration is about 0.75        to about 1.6 parts by weight of base, most preferably about 1.0        to about 1.3 parts by weight of base.    -   e) Formula II-4 at a concentration of about 0 to about 5 parts        by weight of base. Preferably, the concentration is about 0.1 to        about 0.8 parts by weight of base, most preferably about 0.2 to        about 0.6 parts by weight of base.    -   f) Formula VI at a concentration of about 0 to about 2.5 parts        by weight of base. Preferably, the concentration is about 0 to        about 1.0 parts by weight of base, most preferably about 0 to        about 0.5 parts by weight of base. The inhibitor can be mixed        in (1) to tetramethyl divinylsiloxane; (2) tetramethyl        tetravinyl cyclosiloxane; and/or (3) dimethylvinyl terminated        polydimethlysiloxane polymer, and then further blended in about        a 500 centipoise to about 5,000 centipoise dimethylvinyl        terminated polydimethylsiloxane polymer to form an inhibitor        master batch.    -   g) In situ treated fumed silica treated with        hexamethyldilsilazane and tetramethyldivinyldisilazane to form a        surface treated filler with an area of about 200 m² per gram to        about 400 m² per gram at a concentration of about 10 to about 40        parts by weight of base. Preferably, the concentration is about        18 to about 30 parts by weight of base, most preferably about 20        to about 28 parts by weight of base.    -   h) A release agent having the formula M_(x)Q^(OH), where x        ranges from 1 to 3, at a concentration about 0 to about 5 parts        by weight of base. Preferably, the concentration is about 0.2 to        about 1.0 parts by weight of base, most preferably about 0.3 to        about 0.8 parts by weight of base.    -   i) Formula X where R are methyl groups and n ranges from about 4        to about 12, at a concentration of about 0 to about 6 parts by        weight of base. Preferably, the concentration is about 0.2 to        about 1.0 parts by weight of base, most preferably about 0.3 to        about 0.8 parts by weight of base.        For the sake of convenience, the composition ranges of        Formulation 1 listed above are reproduced in tabular form in        TABLE 1, below:

TABLE 1 Formulation 1 Part by Weight of Base More Most ComponentPreferred Preferred Preferred Formula I-5 (vinyl siloxane) 15-90 50-8460-68 Formula I-6 (vinyl siloxane)  0-10 2-6 3-5 Formula I-7 (vinylsiloxane)  0-12 2.5-8   3-6 Formula II-7 (crosslinker) 0-5 0.75-1.6 1.0-1.3 Formula II-4 (crosslinker) 0-5 0.1-0.8 0.2-0.6 Formula VI(inhibitor)   0-2.5   0-1.0   0-0.5 Treated fumed silica with 10-4018-30 20-28 hexamethyldisilazane and tetramethyldivinyldisilazaneRelease agent 0-5 0.2-1.0 0.3-0.8 Formula X (pre-structuring 0-6 0.2-1  0.3-0.8 compound)

Separate from the Formulation 1 base is the catalyst, which can bebetween about 5% to about 15% platinum methylvinyl complex in (1)tetramethyl divinylsiloxane; (2) tetramethyl tetravinyl cyclosiloxane;and/or (3) dimethylvinyl terminated polydimethylsiloxane polymer.Preferably, the catalyst is about 10% platinum methylvinyl complex inany of the above combinations of polymers. The preferred platinummethylvinyl complex is 10% platinum in (1) tetramethyl divinylsiloxane;(2) tetramethyl tetravinyl cyclosiloxane; and/or (3) dimethylvinylterminated polydimethylsiloxane polymer, and then further blended inabout a 500 centipoise to about 5,000 centipoise dimethylvinylterminated polydimethylsiloxane polymer to form a catalyst master batch.The concentration of the platinum catalyst in the catalyst master batchis between about 0.1% and about 2.0%, and preferably between about 0.25%and about 1.0%. The concentration of the Pt catalyst in the LSR processis between about 0.1 ppm to about 20 ppm of base and preferably about 5ppm to about 15 ppm of base. The catalyst/vinyl siloxane polymer blendis fed directly into the LSR mixing/transferring screws, or fed by aninjection into the base feed line. When fed into the base feed line, itis preferably injected into the feed line at a point as close aspracticable to the point at which the base feed line joins the injectionmolding machine barrel.

When using a blend of Formula II-4 and II-7 hydride crosslinkers, theratio of the two cross linkers can be between about 1:6, and preferablyabout 1:3 of Formula II-4 to Formula II-7. Optionally, a single hydridefrom either Formula II-4 or Formula II-7 can be separately used.

Optionally, the inhibitor and a portion of the vinyl siloxane polymerscan be removed from the base to make an inhibitor master batch, whichmay be fed directly into the injection molding machine or fed by aninjector into the base feed line. The concentration of the inhibitor inthe inhibitor master batch is between about 0.1% and about 3.0%, andpreferably between about 0.5% and about 2.5%. This optionalconfiguration allows for greater control when manufacturing parts ofdifferent sizes, cure times, and desired physical properties. These,along with other configurations, are described more fully below.

Additional additives can include: color master batches, UV stabilizers,light stabilizers, self bonding additives, anti-microbial additives,thermal stabilizers, release agents, antistatic additives, flameproofing additives, low compression set additives, durometer adjustmentadditives, oil resistance additives, anti-crepe hardening additives,mold release additives, plasticizers, thickening or consistency increaseadditives, and blowing agents. These additives can either be added: 1)to the liquid silicone rubber base; 2) to the inhibitor master batch; 3)to the catalyst master batch; 4) as a separate feed into the base feedline; or 5) as a separate feed directly into the injection moldingmachine.

Unexpectedly, the injection molding machine transfer screw providessufficient mixing to thoroughly mix the individual components used inthe processes of the present invention. This obviates the need forpremixing, and so obviates the need for expensive equipment to achievepremixing.

Also unexpected with the processes of the present invention was thenearly instantaneous yield of perfectly molded parts upon moldingstart-up, as compared with the standard two-part LSR process start-up,which requires the process to run for 30 to 60 minutes (lining out theprocess) before good parts are obtained. In other words, the processesof the present invention eliminate the waste of time and material thatis inherent in the prior art processes. This is likely due to: 1) thepre-mixed LSR base, which contains vinyl polymer and hydride crosslinkerin appropriate and precise molar ratios; 2) precise and controlledaddition of the inhibitor master batch; and 3) precise and controlledaddition of the catalyst master batch.

The methods for producing the molded silicone rubber product aredescribed below with reference to FIGS. 1-11.

FIG. 1 shows the standard two-part LSR process of the prior art. A basestorage tank 100 is connected to a static mixer 120 via a base feed pump105 and base feed line 106. The base storage tank 100 contains a mixtureof vinyl siloxane polymer, treated amorphous fumed silica, and platinumcatalyst (component A), which is fed to the static mixer 120 via thepump 105. A hydride master batch storage tank 110 is also connected tothe static mixer 120 via a hydride master batch feed pump 115 andhydride master batch feed line 116. The hydride master batch storagetank 110 contains a mixture of vinyl siloxane polymer, treated amorphousfumed silica, hydride crosslinker, and inhibitor (component B), which isfed to the static mixer 120 via the pump 115. The static mixer 120 mixescomponents A and B, while transferring the mixture to an injectionmolding machine 5 at the beginning of the mixer 35. The mixer 35transfers the liquid silicone rubber to an injection shot cavity 40. Theliquid silicone rubber in the shot cavity 40 is then transferred to aheated mold 45, where it is cured at a temperature from about 80° C. toabout 230° C., depending on the mold size, cure specification, anddesired physical properties.

FIG. 2 shows the LSR process of an alternate embodiment, wherein theinhibitor master batch and the catalyst master batch are separate fromthe liquid silicone rubber base. Each of the liquid silicone rubberbase, inhibitor master batch, and catalyst master batch is fedseparately into the base feed line 200, which then feeds into theinjection molding machine barrel 35 at a single entry point. The basestorage tank 1 is connected to the barrel 35 of an injection moldingmachine 5 via a base feed pump 10 and an optional base composition feedrate adjuster 15. The base feed rate can be controlled via base feedpump 10, base feed rate adjuster 15, or a combination of both. The basefeed pump can be any large displacement pump, such as a Graco Bulldog10:1 Transfer Pump. In the configuration of FIG. 2, the liquid siliconerubber base contained in the base storage tank 1 may comprise: a) atleast one vinyl siloxane polymer and at least one hydride crosslinker;b) all the components of a), plus at least one filler; c) all thecomponents of b), plus at least one pre-structuring compound; or d) allthe components of c), plus at least one release agent. The weightpercent of vinyl siloxane polymer mixed with the hydride crosslinker isabout 85% to about 99%, and preferably about 95% to about 99%. Theinhibitor master batch storage tank 50 is connected to the base feedline 200 via an inhibitor master batch feed pump 55, optionally, aninhibitor master batch composition feed rate adjuster 60, and aninhibitor feed line 220. The inhibitor master batch feed pump may be anysmall piston displacement pump, gear pump, micro motion injector pump,or other positive displacement pump. The addition of at least one vinylsiloxane polymer to the inhibitor master batch is optional, butpreferred. If added, the weight percent of vinyl siloxane polymers mixedwith the inhibitor could be subtracted from the vinyl siloxane polymerscontained in the base. Thus, the total weight percent of vinyl siloxanepolymers would remain constant. Generally, the weight percent ofinhibitors mixed with the vinyl siloxane polymers is about 0.1% to about3.0%, and preferably about 0.5% to about 2.5%. Removing the inhibitorfrom the base allows for greater operator control when making differentmolded parts. Similarly, the catalyst storage tank 20 is also connectedto the base feed line 200 via a catalyst feed pump 25, an optionalcatalyst feed rate adjuster 30, and a catalyst feed line 210. Thecatalyst fed rate can be controlled via catalyst feed pump 25, catalystfeed rate adjuster 30, or a combination of both. The catalyst feed pumpmay be any small piston displacement pump, gear pump, micro motioninjector pump, or other positive displacement pump. Generally, theweight percent of platinum catalyst mixed with at least one vinylsiloxane polymer is about 0.1% to about 3.0%, and preferably about 1.0%.Upon delivery to the injection molding machine barrel 35 by the basefeed line 200, the liquid silicone rubber base, inhibitor master batch,and catalyst master batch are mixed in said barrel 35 by operation ofthe injection molding machine 5.

FIG. 3 shows another preferred embodiment, similar to that shown in FIG.2, except that the base feed line 200 feeds into a mixer 130 after—orbelow the point at which—inhibitor master batch enters the base feedline 200 via inhibitor feed line 220 and before—or above the point atwhich—catalyst master batch enters the base feed line 200 via catalystfeed line 210. In this way, the liquid silicone rubber base from thebase storage tank 1 and the inhibitor master batch from the inhibitormaster batch storage tank 50 are mixed in the mixer. The mixer may beeither a static mixer, a dynamic mixer, or an “orifice” as describedabove.

FIG. 4 shows another preferred embodiment, similar to that shown in FIG.3, except that the base feed line 200 feeds into a mixer 135 after—orbelow the point at which—catalyst master batch enters the base feed line200 via catalyst feed line 210. In this way, the liquid silicone rubberbase from the base storage tank 1, the inhibitor master batch from theinhibitor master batch storage tank 50, and the catalyst master batchfrom the catalyst master batch storage tank 20 are mixed in the mixer.The mixer may be either a static mixer, a dynamic mixer, or an “orifice”as described above.

FIG. 5 shows another preferred embodiment, similar to that shown inFIGS. 3 and 4, except that the base feed line 200 feeds into a firstmixer 130 after—or below the point at which—inhibitor master batchenters the base feed line 200 via inhibitor feed line 220 and before—orabove the point at which—catalyst master batch enters the base feed line200 via catalyst feed line 210. Subsequently, the base feed line 200feeds into a second mixer 135 after—or below the point at which—catalystmaster batch enters the base feed line 200 via catalyst feed line 210.In this way, the liquid silicone rubber base from the base storage tank1 and the inhibitor master batch from the inhibitor master batch storagetank 50 are mixed in the first mixer, which may be either a staticmixer, a dynamic mixer, or an “orifice” as described above, and thecatalyst master batch from the catalyst master batch storage tank 20 isthen mixed with the liquid silicone rubber base and inhibitor masterbatch mixture by the second mixer 135 which, independently from thefirst mixer 130, may be either a static mixer, a dynamic mixer, or an“orifice” as described above.

FIG. 6 shows another preferred embodiment, wherein the catalyst masterbatch is separate from the liquid silicone rubber base, which containsinhibitor. The liquid silicone rubber base and catalyst master batch arefed separately into the base feed line 200, which then feeds into theinjection molding machine barrel 35 at a single entry point. The basestorage tank 1 is connected to the barrel 35 of an injection moldingmachine 5 via a base feed pump 10, an optional base composition feedrate adjuster 15, and the base feed line 200. The base feed rate can becontrolled via base feed pump 10, base feed rate adjuster 15, or acombination of both. The base feed pump can be any large displacementpump, such as a Graco Bulldog 10:1 Transfer Pump. In the configurationof FIG. 6, the liquid silicone rubber base contained in the base storagetank 1 may comprise: a) at least one vinyl siloxane polymer, at leastone hydride crosslinker, and at least one liquid injection moldinginhibitor; b) all the components of a), plus at least one filler; c) allthe components of b), plus at least one pre-structuring compound; d) allthe components of c), plus at least one release agent; or e) at leastone hydride crosslinker with at least one liquid injection moldinginhibitor. If the liquid silicone rubber base comprises both at leastone vinyl siloxane polymer and at least one hydride crosslinker, thenthe weight percent of vinyl siloxane polymer mixed with the hydridecrosslinker is about 85% to about 99%, and preferably about 95% to about99%. The catalyst storage tank 20 is connected to the base feed line 200via a catalyst feed pump 25, an optional catalyst feed rate adjuster 30,and a catalyst feed line 210. The catalyst fed rate can be controlledvia catalyst feed pump 25, catalyst feed rate adjuster 30, or acombination of both. The catalyst feed pump may be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump. Generally, the weight percent of platinumcatalyst mixed with the vinyl siloxane polymer is about 0.1% to about3.0%, and preferably about 1.0%. Upon delivery to the injection moldingmachine barrel 35 by the base feed line 200, the liquid silicone rubberbase and catalyst master batch are mixed in said barrel 35 by operationof the injection molding machine 5.

FIG. 7 shows another preferred embodiment, similar to that shown in FIG.6, except that the base feed line 200 feeds into a mixer 135 after—orbelow the point at which—catalyst master batch enters the base feed line200 via catalyst feed line 210. In this way, the liquid silicone rubberbase from the base storage tank 1 and the catalyst master batch from thecatalyst master batch storage tank 20 are mixed in the mixer. The mixermay be either a static mixer, a dynamic mixer, or an “orifice” asdescribed above. As with the configuration of FIG. 6, in theconfiguration of FIG. 7 the liquid silicone rubber base contained in thebase storage tank 1 may comprise: a) at least one vinyl siloxanepolymer, at least one hydride crosslinker, and at least one liquidinjection molding inhibitor; b) all the components of a), plus at leastone filler; c) all the components of b), plus at least onepre-structuring compound; d) all the components of c), plus at least onerelease agent; or e) at least one hydride crosslinker with at least oneliquid injection molding inhibitor. If the liquid silicone rubber basecomprises both at least one vinyl siloxane polymer and at least onehydride crosslinker, then the weight percent of vinyl siloxane polymermixed with the hydride crosslinker is about 85% to about 99%, andpreferably about 95% to about 99%.

FIG. 8 shows the LSR process of an alternate embodiment. The basestorage tank 1 is connected to an injection molding machine 5 via a basefeed pump 10, an optional base composition feed rate adjuster 15, and abase feed line 200. The base feed rate can be controlled via base feedpump 10, base feed rate adjuster 15, or a combination of both. The basefeed pump can be any large displacement pump, such as a Graco Bulldog10:1 Transfer Pump. Similarly, the catalyst storage tank 20 is connectedto the injection molding machine 5 via a catalyst feed pump 25, anoptional catalyst feed rate adjuster 30, and a catalyst feed line 210.The catalyst fed rate can be controlled via catalyst feed pump 25,catalyst feed rate adjuster 30, or a combination of both. The catalystfeed pump may be any small piston displacement pump, gear pump, micromotion injector pump, or other positive displacement pump. Generally,the weight percent of platinum catalyst mixed with the vinylsiloxanepolymer is about 0.1% to about 3.0%, and preferably about 1.0%.

During operation, the base feed pump 10 transfers the vinyl siloxanepolymer, hydride crosslinker, inhibitor, and optional filler andpre-structuring compound containing base to the injection moldingmachine at the beginning of the mixer 35. Once the base enters theinjection molding machine 5 via the base feed line 200, the catalystfeed pump 25 begins transferring the catalyst to the injection moldingmachine at the beginning of the mixer 35 via the catalyst feed line 210.The mixer 35 mixes the base and catalyst, while transferring the liquidsilicone rubber to an injection shot cavity 40. The liquid siliconerubber in the shot cavity 40 is then transferred to a heated mold 45,where it is cured at a temperature from about 80° C. to about 230° C.,depending on the mold size, cure specification, and desired physicalproperties. The proportion in which the base and catalyst are mixed canbe adjusted as needed by the feed rate adjusters 15 and 30, the pumps 10and 25, or a combination of both.

FIG. 9 shows another preferred embodiment, wherein the inhibitor may beremoved from the base and separately fed into the mixer 35. Theinhibitor master batch storage tank 50 is connected to the injectionmolding machine 5 via an inhibitor master batch feed pump 55, anoptional inhibitor master batch composition feed rate adjuster 60, andan inhibitor feed line 220. The inhibitor master batch feed pump may beany small piston displacement pump, gear pump, micro motion injectorpump, or other positive displacement pump. The weight percent of vinylsiloxane polymers mixed with the inhibitor could be subtracted from thevinyl siloxane polymers contained in the base. Thus, the total weightpercent of vinyl siloxane polymers would remain constant. Generally, theweight percent of inhibitors mixed with the vinyl siloxane polymers isabout 0.1% to about 3.0%, and preferably about 0.5% to about 2.5%.Removing the inhibitor from the base allows for greater operator controlwhen making different molded parts. As described above, the mixer may beeither a static mixer or screw type mixer (not shown), or the same screwmixer used in the injection molding machine 5.

FIG. 10 is a further embodiment, where a separate feed of a portion ofthe vinyl siloxane polymers may be connected to the mixer 35. The vinylsiloxane polymer storage tank 65 is connected to the injection moldingmachine 5 via a vinyl siloxane polymer feed pump 70, an optionalcomposition feed rate adjuster 75, and a vinyl siloxane polymer feedline 230. The vinyl siloxane polymer feed pump may be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump. Further, as described in FIG. 10, theinhibitor is removed from the base. This allows the operator to vary theamount of inhibitor while keeping the weight percent of vinyl siloxanepolymers constant via the separate feed pump 70.

FIG. 11 is a variation of the above, where the separate vinyl siloxanepolymer feed line 230 is fed into the inhibitor feed line 220 prior tointroduction into the mixer 35. These two configurations allow for evengreater operator control.

FIG. 12 shows the LSR process of an alternate embodiment, wherein theinhibitor master batch and the catalyst master batch are separate fromthe liquid silicone rubber base. Each of the liquid silicone rubberbase, inhibitor master batch, and catalyst master batch is fedseparately into the base feed line 200, which then feeds into theinjection molding machine barrel 35 at a single entry point. The basestorage tank 1 is connected to the barrel 35 of an injection moldingmachine 5 via a base feed pump 10 and an optional base composition feedrate adjuster 15. The base feed rate can be controlled via base feedpump 10, base feed rate adjuster 15, or a combination of both. The basefeed pump can be any large displacement pump, such as a Graco Bulldog10:1 Transfer Pump. In the configuration of FIG. 12, the liquid siliconerubber base contained in the base storage tank 1 may comprise: a) atleast one vinyl siloxane polymer and at least one hydride crosslinker;b) all the components of a), plus at least one filler; c) all thecomponents of b), plus at least one pre-structuring compound; or d) allthe components of c), plus at least one release agent. The weightpercent of vinyl siloxane polymer mixed with the hydride crosslinker isabout 85% to about 99%, and preferably about 95% to about 99%. Theinhibitor master batch storage tank 50 is connected to the base feedline 200 via an inhibitor master batch feed pump 55, optionally, aninhibitor master batch composition feed rate adjuster 60, and aninhibitor feed line 220. The inhibitor master batch feed pump may be anysmall piston displacement pump, gear pump, micro motion injector pump,or other positive displacement pump. The addition of at least one vinylsiloxane polymer to the inhibitor master batch is optional, butpreferred. If added, the weight percent of vinyl siloxane polymers mixedwith the inhibitor could be subtracted from the vinyl siloxane polymerscontained in the base. Thus, the total weight percent of vinyl siloxanepolymers would remain constant. Generally, the weight percent ofinhibitors mixed with the vinyl siloxane polymers is about 0.1% to about3.0%, and preferably about 0.5% to about 2.5%. Removing the inhibitorfrom the base allows for greater operator control when making differentmolded parts. The additive storage tank 21 is also connected to the basefeed line 200 via an additive feed pump 26, an optional additive feedrate adjuster 31, and an additive feed line 211. The additive feed ratecan be controlled via additive feed pump 26, additive feed rate adjuster31, or a combination of both. The additive feed pump 26 may be any smallpiston displacement pump, gear pump, micro motion injector pump, orother positive displacement pump. The additive may be selected from thegroup consisting of color master batches, UV stabilizers, lightstabilizers, self bonding additives, anti-microbial additives, thermalstabilizers, release agents, antistatic additives, flame proofingadditives, low compression set additives, durometer adjustmentadditives, oil resistance additives, anti-crepe hardening additives,mold release additives, plasticizers, thickening or consistency increaseadditives, blowing agents, and combinations thereof. Similarly, thecatalyst storage tank 20 is also connected to the base feed line 200 viaa catalyst feed pump 25, an optional catalyst feed rate adjuster 30, anda catalyst feed line 210. The catalyst feed rate can be controlled viacatalyst feed pump 25, catalyst feed rate adjuster 30, or a combinationof both. The catalyst feed pump 25 may be any small piston displacementpump, gear pump, micro motion injector pump, or other positivedisplacement pump. Generally, the weight percent of platinum catalystmixed with at least one vinyl siloxane polymer is about 0.1% to about3.0%, and preferably about 1.0%. Upon delivery to the injection moldingmachine barrel 35 by the base feed line 200, the liquid silicone rubberbase, inhibitor master batch, additive, and catalyst master batch aremixed in said barrel 35 by operation of the injection molding machine 5.

FIG. 13 shows another preferred embodiment, similar to that shown inFIG. 12, except that the base feed line 200 feeds into a mixer 135after—or below the point at which—catalyst master batch enters the basefeed line 200 via catalyst feed line 210. In this way, the liquidsilicone rubber base from the base storage tank 1, the inhibitor masterbatch from the inhibitor master batch storage tank 50, the additive fromthe additive master batch storage tank 21, and the catalyst master batchfrom the catalyst master batch storage tank 20 are mixed in the mixer.The mixer may be either a static mixer, a dynamic mixer, or an “orifice”as described above.

FIG. 14 shows another preferred embodiment, similar to that shown inFIG. 13, except that the base feed line 200 feeds into a mixer 130after—or below the point at which—inhibitor master batch and theadditive master batch enter the base feed line 200 via inhibitor feedline 220 and additive feed line 211 (respectively) and before—or abovethe point at which—catalyst master batch enters the base feed line 200via catalyst feed line 210. In this way, the liquid silicone rubber basefrom the base storage tank 1, the inhibitor master batch from theinhibitor master batch storage tank 50, and the additive master batchfrom the additive master batch storage tank are mixed in the mixer 130.The mixer may be either a static mixer, a dynamic mixer, or an “orifice”as described above. Then, as in FIG. 13, the base feed line 200 feedsinto a mixer 135 after—or below the point at which—catalyst master batchenters the base feed line 200 via catalyst feed line 210.

FIG. 15 shows another preferred embodiment, similar to that shown inFIG. 14, except that the base feed line 200 feeds into a mixer 131after—or below the point at which—inhibitor master batch enters the basefeed line 200 via inhibitor feed line 220 and before—or above the pointat which—the additive master batch and the catalyst master batch enterthe feed line 200 via additive feed line 211 and catalyst feed line 210,respectively. In this way, the liquid silicone rubber base from the basestorage tank 1 and the inhibitor master batch from the inhibitor masterbatch storage tank 50 are mixed in the mixer 131. The mixer may beeither a static mixer, a dynamic mixer, or an “orifice” as describedabove. Then, as in FIG. 14, the base feed line 200 feeds into a mixer130 after—or below the point at which—additive master batch enters thebase feed line 200 via additive feed line 211 and before—or above thepoint at which—catalyst master batch enters the base feed line 200 viacatalyst feed line 210.

As will be appreciated by those having ordinary skill in the relevantart, the mixers 130, 131, and 135 can be varied beyond what is shown bythe figures. For example, FIGS. 13-15 show the relative positions ofmixers 130, 131, and 135. One of ordinary skill in the art willrecognize readily that (for example) the arrangement of mixers in FIG.15 may be altered to eliminate mixer 135 alone, mixer 130 alone, bothmixers 130 and 135, or both mixers 131 and 135; these arrangements ofmixers are within the scope of the present invention.

The base compositions described above, along with the introduction ofthe catalyst, inhibitor, and/or hydride cross linker at the point ofmixing, decreases part variability, improves quality, shortens curetime, and lowers equipment costs. It also allows the curing rate of theliquid silicone rubber and the physical properties of the cured siliconerubber to be readily adjusted by modifying the ratio of base, catalyst,inhibitor, and/or hydride cross linker.

Example 1 Physical Properties of a Standard Liquid Silicone Rubber Sheet

This EXAMPLE 1 describes the physical properties of a ASTM D395 standard6 inch by 6 inch by 0.075 inch liquid silicone rubber sheet cured at 5minutes at 350° F. using Formulation 1 at various concentrations ofinhibitor, and compares them against the physical properties of anidentical sheet obtained via a standard two part LSR process thatemployed the same components in Formulation 1 and 100% inhibitor. Thedata are shown in TABLE 2, below:

TABLE 2 Standard Single LSR Single LSR Two- Base with Base with SingleLSR Physical Part LSR 100% of 50% of Base with 25% Properties Processthe Inhibitor the Inhibitor of the Inhibitor Duro (Shore A) 49 47 48 49Tear (lb/in) 270 279 302 297 Tensile (lb/in²) 1375 1403 1347 1282Elongation (%) 610 547 689 637 100% Modulus 324 345 276 288 (lb/in²)200% Modulus 528 566 469 486 (lb/in²) 300% Modulus 709 771 625 650(lb/in²)As can be seen from TABLE 2, by using a single LSR base containingpre-mixed vinyl polymer, and silica, with varying concentrations ofinhibitor (25%, 50%, and 100% of the inhibitor concentration found inthe standard two-part LSR process), and by adding the catalystseparately, the virtually same heat cured physical properties may beobtained.

Example 2 MDR Cure Profile

This EXAMPLE 2 describes the MDR cure profile at 115° C. usingFormulation 1 at various concentrations of inhibitor, compared to theMDR cure profile of a standard two part LSR process using the samecomponents in Formulation 1 and 100% inhibitor. The data are shown inTABLE 3, below:

TABLE 3 Standard Single LSR Single LSR MDR Cure Two- Base with Base withSingle LSR Profile at Part LSR 100% of 50% of Base with 25% 115° C.Process the Inhibitor the Inhibitor of the Inhibitor t₂ (min.) 0.88 0.470.29 0.22 t₁₀ (min.) 0.98 0.55 0.36 0.29 t₅₀ (min.) 1.15 0.69 0.47 0.39t₉₀ (min.) 1.75 0.95 0.63 0.50 Time at peak 1.22 0.78 0.57 0.49 rate(min.) Peak rate 30.69 34.56 38.65 43.27 (in.-lbs./min.) MH (in.-lbs.)13.31 12.75 11.51 11.60 ML (in.-lbs.) 0.01 0.00 0.00 0.02As shown by the data of TABLE 3, the cure rates are readily modified byaltering the inhibitor concentration. As used above, “t_(x)”, where “x”is an integer, denotes the time required to obtain “x”% of the totalcure or crosslinking, expressed in minutes.

Taken together, the data of TABLE 2 and TABLE 3 demonstrate theunexpected result that the compositions and methods of the presentinvention provide the end user with a wide range of cure times (TABLE 3)without concomitant sacrifice of physical properties (TABLE 2).

Example 3 Molding Trial: Silicone Rubber Cap

This EXAMPLE 3 is a molding trial of a 183 gram silicone rubber cap witha diameter of 3¼ inches and a height of 2¼ inches. The normal productioncycle time and temperature using a standard two part LSR process was 250seconds at 300° F. Using the 50% inhibitor single LSR base ofFormulation 1, the cycle time at 300° F. was reduced from 250 seconds to150 seconds without the need for any postbaking. Below 150 seconds—to aslow as 75 seconds—a good cure could be achieved throughout the thickestsection of this part with postbaking for 5 minutes at 400° F., with nosign of deformation.

Example 4 Molding Trial: 96-Well Silicone Rubber Pad

This EXAMPLE 4 is a molding trial of a 96-well silicone rubber pad witha length of 4.41 inches, a width of 3 inches, and 96 individual 0.37inch thick nubs extending out of the thin base. The standard two partLSR production cycle for this part was 35 seconds at 270° F. With thesingle Formulation 1 LSR base with 50% inhibitor, the cure time wasdecreased to 4 seconds at a temperature of 375° F. Further, the overallcycle time per part was reduced to 24 seconds, compared to 60 secondswith the standard two part LSR process.

Example 5 Molding Trial: Breast Pump Diaphragm

This EXAMPLE 5 is a molding trial of a 15.7 gram LSR silicone rubberdiaphragm for a baby's milk breast pump produced in an eight cavity coldrunner mold in which eight parts are automatically removed from the moldeach injection molding cycle. The normal total production cycle using astandard two part LSR product is 50.7 seconds at 325° F. Using thesingle Formulation 1 LSR Base with 25% inhibitor, the total cycle timewas decreased to 30.7 seconds at 325° F. without the need for any postbaking. This results in a forty percent increase in cured product outputand a 24% cost/part savings when all factors are taken intoconsideration.

In addition to the reduced molding cycle times, this system offers theadvantages of a single Base with the vinyl and hydride componentspremixed. This eliminates a pump and the LSR A & B pumping and mixingvariability and errors, as well as, control of the cure speed byenabling the molder to control the inhibitor level at the injectionmolding machine. In summary, this invention represents a moreconsistent, faster method of producing silicone molded LSR parts.

Example 6 Molding Trials Comparison

This EXAMPLE 6 describes and compares the properties of silicone partsproduced via standard two-part LSR techniques and a process of thepresent invention. As shown by TABLE 4, below, the production of partswith a wide range of dimensions and weights was compared. The durometer(hardness) of the silicone materials used varied from 20 to 70 Shore A.

TABLE 4 Solid Food Cushion Cushion Silicone Prepartion Pump Medical capw/o Cap w/ Rubber Part Diaphram Bulb Post-bake Post-bake Tube PartHeight (cm) 8.0 2.8 9.3 2.7 2.7 — Width (cm) 5.0 5.8 — 5.5 5.5 —Thickness (cm) 0.25 — — — — — Diameter (cm) — 6.7 5.9 6.8 6.8 4.0 Length(cm) — — — — — 24.5 Part Weight (g) 23.7 15.6 47.4 181.4 181.4 422.4Durometer 70 50 50 50 50 20 (Shore A) Standard Two- 42 51 32 235 200 249Part LSR Molding Cycle Time (seconds) LSR Select 19 31 15 150 95 175Molding Cycle Time (seconds) Cycle Time 55.0 39.2 53.1 36.2 52.5 29.7Reduction (%) Inhibitor Level 27.5 6.25 6.25 6.25 6.25 50.0 (% of stdLSR)The key results are the differences in actual production environmentmolding cycles between the Standard Two-Part LSR Molding Cycle and theLSR Select Molding Cycle. Depending upon the part and the equipmentused, the cycle time reduction was between 29.7% and 55%. Cycle timereduction is only one of the advantages of the present invention. Inaddition, one obtains via the materials and methods of the presentinvention: higher-quality parts, less waste, elimination ofroom-temperature pot life issues, and enhanced parts productionconsistency.

The faster cure speed, as shown in TABLE 4, is due to the controlledreduction of the inhibitor level in the system. The bottom row of thechart, labelled “Inhibitor Level (% of std LSR),” shows that theinhibitor can be reduced to only 6.25% of what is normally added to astandard two-part LSR molding cycle. Depending upon the part size,however, higher amounts of inhibitor are added (e.g., 27.5% and 50% ofthe standard amount), yet this higher amount is still less than what isused in standard two-part LSR molding systems (even the very large 422 gpart—column labelled “Solid Silicone Rubber Tube Part” of TABLE 4—whichrequires a long mold filling time. In sum, the compositions and methodsof the present invention provide the user with much greater control overthe molding process than standard two-part LSR molding cycles of theprior art, which employ set inhibitor levels.

All references cited in this specification are herein incorporated byreference as though each reference was specifically and individuallyindicated to be incorporated by reference. The citation of any referenceis for its disclosure prior to the filing date and should not beconstrued as an admission that the present invention is not entitled toantedate such reference by virtue of prior invention.

It will be understood that each of the elements described above, or twoor more together may also find a useful application in other types ofmethods differing from the type described above. Without furtheranalysis, the foregoing will so fully reveal the gist of the presentinvention that others can, by applying current knowledge, readily adaptit for various applications without omitting features that, from thestandpoint of prior art, fairly constitute essential characteristics ofthe generic or specific aspects of this invention set forth in theappended claims. The foregoing embodiments are presented by way ofexample only; the scope of the present invention is to be limited onlyby the following claims.

1. A method for producing a molded silicone rubber product comprising:a) feeding into a base feed line a liquid silicone rubber basecomprising: i) at least one vinyl siloxane polymer; and ii) at least onehydride crosslinker; b) feeding into a catalyst feed line a catalystmaster batch comprising: i) at least one catalyst; and ii) optionally,at least one vinyl siloxane polymer; c) optionally feeding into anoptional inhibitor feed line an optional inhibitor master batchcomprising: i) at least one liquid injection molding inhibitor; and ii)optionally, at least one vinyl siloxane polymer; d) optionally feedinginto an optional additive feed line an optional at least one additive;e) directing said liquid silicone rubber base and said catalyst masterbatch, optionally directing said optional inhibitor master batch, andoptionally directing said optional at least one additive into the barrelof an injection molding machine; f) operating said injection moldingmachine, thereby mixing said liquid silicone rubber base, said catalystmaster batch, said optional inhibitor master batch, and said optional atleast one additive; and g) curing said mixed liquid silicone rubberbase, catalyst master batch, optional inhibitor master batch, andoptional at least one additive by heating.
 2. The method of claim 1,wherein said at least one vinyl siloxane polymer of said liquid siliconerubber base, said catalyst master batch, and said optional inhibitormaster batch are independently selected from the group consisting of:

and combinations thereof, wherein: a) the radical R are, independently,selected from the group consisting of monovalent hydrocarbon radicalsand halogenated monovalent hydrocarbon radicals; b) the radical R¹ are,independently, selected from the group consisting of phenyl, loweralkenyl of 2 to 8 carbon atoms, lower alkyl of 1 to 8 carbon atoms andmononuclear aryl radicals; c) the radical R² are, independently,selected from the group consisting of an alkyl radical, a mononucleararyl radical, a lower alkyl radical of 1 to 8 carbon atoms, a phenylradical, lower alkenyl of 2 to 8 carbon atoms, and a vinyl group; d) theradical R″ are, independently, selected from the same groups as theradical R¹; e) Vi denotes vinyl; f) m is an integer from about 100 toabout 10,000; g) n is an integer from about 100 to about 400; h) o is aninteger from about 2 to about 8; i) p is an integer from about 100 toabout 200; j) q is an integer from about 5 to about 15; k) w is aninteger from about 0 to about 500; l) x is an integer from about 100 toabout 10,000; m) y is an integer from about 0 to about 300; and n) z isan integer from about 0 to about
 200. 3. The method of claim 2, whereinsaid at least one hydride crosslinker is selected from the groupconsisting of:

and combinations thereof, wherein: a) each R⁴ is selected,independently, from the group consisting of hydrogen, monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals;b) each R⁵ radical is selected, independently, from the group consistingof monovalent hydrocarbon radicals, and halogenated monovalenthydrocarbon radicals; c) s is an integer from about 1 to about 1000; d)t is an integer from about 5 to about 200; e) u is an integer from about14 to about 30; f) v is an integer from about 12 to about 21; g) w is aninteger from about 2 to about 8; h) x is an integer from about 3 toabout 9; i) y is an integer from about 5 to about 15; j) M ismonofunctional trimethylsilyl or (CH₃)₃SiO_(1/2); k) H is hydrogen; andl) Q is tetrafunctional silicon dioxide or SiO_(4/2).
 4. The method ofclaim 3, wherein said at least one catalyst is a platinum complex formedfrom a reaction between H₂PtCl₆+6H₂O+ dimethyl vinyl terminatedpolydimethylsiloxane polymer.
 5. The method of claim 4, wherein said atleast one liquid injection molding inhibitor of said optional inhibitormaster batch is selected from the group consisting of:

and combinations thereof, wherein: a) R¹ has the formula:—R³—C≡C—R⁴  (Formula IV); b) R² is selected from the group consistingof: —R³—C≡C—R⁴ (Formula IV); hydrogen; triorganosilyl radicals;siloxanes; and

c) R³ is selected from the group consisting of: of divalenthydrocarbonradicals consisting of linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; linear or branched alkenylradicals having from about 1 to about 10 carbon atoms; linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;cycloalkyl radicals having from about 3 to about 12 carbon atoms;cycloalkenyl radicals having from about 3 to about 12 carbon atoms;cycloalkynyl radicals having from about 8 to about 16 carbon atoms;fluorinated linear or branched alkyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;hydrocarbonoxy radicals containing at least two carbon atoms;fluorinated hydrocarbonoxy radicals containing at least two carbonatoms; chlorinated hydrocarbonoxy radicals containing at least twocarbon atoms; brominated hydrocarbonoxy radicals containing at least twocarbon atoms; aryl radicals; linear or branched alkyl aryl radicals;fluorinated aryl radicals; chlorinated aryl radicals; brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; and brominated linear or branched alkyl-,alkenyl-, or alkynyl aryl radicals; d) R⁴ is selected from the group ofmonovalent radicals consisting of: hydrogen, linear or branched alkylradicals having from about 1 to about 10 carbon atoms; linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;linear or branched alkynyl radicals having from about 1 to about 10carbon atoms; cycloalkyl radicals having from about 3 to about 12 carbonatoms; cycloalkenyl radicals having from about 3 to about 12 carbonatoms; cycloalkynyl radicals having from about 8 to about 16 carbonatoms; fluorinated linear or branched alkyl radicals having from about 1to about 10 carbon atoms; chlorinated linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;hydrocarbonoxy radicals containing at least two carbon atoms;fluorinated hydrocarbonoxy radicals containing at least two carbonatoms; chlorinated hydrocarbonoxy radicals containing at least twocarbon atoms; brominated hydrocarbonoxy radicals containing at least twocarbon atoms aryl radicals; linear or branched alkyl aryl radicals;fluorinated aryl radicals; chlorinated aryl radicals; brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; brominated linear or branched alkyl-, alkenyl-,or alkynyl aryl radicals; and triorganosilyl radicals; and e) R isselected from the group consisting of: hydrogen; alkyl; phenyl; andC_(x)H_(y), where x is an integer from about 2 to about 10, and y is aninteger from about 4 to about
 21. 6. The method of claim 5, wherein saidoptional at least one additive is selected from the group consisting ofcolor master batches, UV stabilizers, light stabilizers, self bondingadditives, anti-microbial additives, thermal stabilizers, releaseagents, antistatic additives, flame proofing additives, low compressionset additives, durometer adjustment additives, oil resistance additives,anti-crepe hardening additives, mold release additives, plasticizers,thickening or consistency increase additives, blowing agents, andcombinations thereof.
 7. The method of claim 1, wherein said liquidsilicone rubber base further comprises at least one filler.
 8. Themethod of claim 7, wherein said filler is in situ treated fumed silicatreated with hexamethyldisilazane and tetramethyldivinyldisilazane. 9.The method of claim 7, wherein said liquid silicone rubber base furthercomprises at least one pre-structuring compound.
 10. The method of claim9, wherein said at least one pre-structuring compound has the formula:

wherein: a) R is selected from the group consisting of monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals;and b) n is an integer from about 0 to about
 12. 11. The method of claim9, wherein said liquid silicone rubber base further comprises at leastone release agent.
 12. The method of claim 11, wherein said at least onerelease agent has the formula M_(x)Q^(OH), wherein x is an integer fromabout 1 to about
 3. 13. The method of claim 11, wherein said base feedline feeds into the barrel of the injection molding machine, and saidcatalyst feed line feeds into said base feed line.
 14. The method ofclaim 13, wherein said liquid silicone rubber base further comprises atleast one liquid injection molding inhibitor.
 15. The method of claim14, wherein said optional inhibitor feed line feeds into the base feedline.
 16. The method of claim 15, wherein said optional additive feedline feeds into the base feed line.
 17. The method of claim 16, whereinafter the catalyst feed line, the optional inhibitor feed line, and theoptional additive feed line have fed into the base feed line, the basefeed line feeds into a mixer.
 18. The method of claim 1, wherein saidbase feed line feeds into the barrel of the injection molding machine,and said catalyst feed line feeds into said base feed line.
 19. Themethod of claim 18, wherein said liquid silicone rubber base furthercomprises at least one liquid injection molding inhibitor.
 20. Themethod of claim 19, wherein said optional inhibitor feed line feeds intothe base feed line.
 21. The method of claim 20, wherein said optionaladditive feed line feeds into the base feed line.
 22. The method ofclaim 21, wherein after the catalyst feed line, the optional inhibitorfeed line, and the optional additive feed line have fed into the basefeed line, the base feed line feeds into a mixer.
 23. The method ofclaim 1, wherein: a) the base feed line feeds separately into the barrelof the injection molding machine; b) the catalyst feed line feedsseparately into the barrel of the injection molding machine; c) theoptional inhibitor feed line feeds separately into the barrel of theinjection molding machine; and d) the optional additive feed line feedsseparately into the barrel of the injection molding machine.
 24. Aliquid silicone rubber base comprising: a) at least one vinyl siloxanepolymer; b) at least one hydride crosslinker; c) at least one filler; d)at least one pre-structuring compound; e) at least one release agent;and f) optionally, at least one injection molding inhibitor; but g) nocatalyst.
 25. The liquid silicone rubber base of claim 24, wherein: a)said at least one vinyl siloxane polymer is selected from the groupconsisting of:

and combinations thereof wherein: i) the radical R are, independently,selected from the group consisting of monovalent hydrocarbon radicalsand halogenated monovalent hydrocarbon radicals; ii) the radical R¹ are,independently, selected from the group consisting of phenyl, loweralkenyl of 2 to 8 carbon atoms, lower alkyl of 1 to 8 carbon atoms andmononuclear aryl radicals; iii) the radical R² are, independently,selected from the group consisting of an alkyl radical, a mononucleararyl radical, a lower alkyl radical of 1 to 8 carbon atoms, a phenylradical, lower alkenyl of 2 to 8 carbon atoms, and a vinyl group; iv)the radical R″ are, independently, selected from the same groups as theradical R¹; v) Vi denotes vinyl; vi) m is an integer from about 100 toabout 10,000; vii) n is an integer from about 100 to about 400; viii) ois an integer from about 2 to about 8; ix) p is an integer from about100 to about 200; x) q is an integer from about 5 to about 15; xi) w isan integer from about 0 to about 500; xii) x is an integer from about100 to about 10,000; xiii) y is an integer from about 0 to about 300;and xiv) z is an integer from about 0 to about 200; b) said at least onehydride crosslinker is selected from the group consisting of:

and combinations thereof, wherein: i) each R⁴ is selected,independently, from the group consisting of hydrogen, monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals;ii) each R⁵ radical is selected, independently, from the groupconsisting of monovalent hydrocarbon radicals, and halogenatedmonovalent hydrocarbon radicals; iii) s is an integer from about 1 toabout 1000; iv) t is an integer from about 5 to about 200; v) u is aninteger from about 14 to about 30; vi) v is an integer from about 12 toabout 21; vii) w is an integer from about 2 to about 8 viii) x is aninteger from about 3 to about 9; ix) y is an integer from about 5 toabout 15; x) M is monofunctional trimethylsilyl or (CH₃)₃SiO_(1/2); xi)H is hydrogen; and xii) Q is tetrafunctional silicon dioxide orSO_(4/2;) c) said at least one filler is in situ treated fumed silicatreated with hexamethyldisilazane and tetramethyldivinyldisilazane; d)said at least one pre-structuring compound has the formula:

wherein: i) R is selected from the group consisting of monovalenthydrocarbon radicals, and halogenated monovalent hydrocarbon radicals;and ii) n is an integer from about 0 to about 12; e) said at least onerelease agent has the formula M_(x)Q^(OH), wherein x is an integer fromabout 1 to about 3; and f) said optional at least one liquid injectionmolding inhibitor is present at a concentration of about 0.0 parts per100 to about 1.4 parts per 100, and is selected from the groupconsisting of:

and combinations thereof, wherein: i) R¹ has the formula:—R³—C≡C—R⁴; ii) R² is selected from the group consisting of: —R³—C≡C—R⁴;hydrogen; triorganosilyl radicals; siloxanes;

combinations thereof wherein: iii) R³ is selected from the groupconsisting of: of divalent hydrocarbonradicals consisting of linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;linear or branched alkenyl radicals having from about 1 to about 10carbon atoms; linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; cycloalkyl radicals having from about 3 to about12 carbon atoms; cycloalkenyl radicals having from about 3 to about 12carbon atoms; cycloalkynyl radicals having from about 8 to about 16carbon atoms; fluorinated linear or branched alkyl radicals having fromabout 1 to about 10 carbon atoms; chlorinated linear or branched alkylradicals having from about 1 to about 10 carbon atoms; brominated linearor branched alkyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;hydrocarbonoxy radicals containing at least two carbon atoms;fluorinated hydrocarbonoxy radicals containing at least two carbonatoms; chlorinated hydrocarbonoxy radicals containing at least twocarbon atoms; brominated hydrocarbonoxy radicals containing at least twocarbon atoms; aryl radicals; linear or branched alkyl aryl radicals;fluorinated aryl radicals; chlorinated aryl radicals; brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; and brominated linear or branched alkyl-,alkenyl-, or alkynyl aryl radicals; iv) R⁴ is selected from the group ofmonovalent radicals consisting of: hydrogen, linear or branched alkylradicals having from about 1 to about 10 carbon atoms; linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;linear or branched alkynyl radicals having from about 1 to about 10carbon atoms; cycloalkyl radicals having from about 3 to about 12 carbonatoms; cycloalkenyl radicals having from about 3 to about 12 carbonatoms; cycloalkynyl radicals having from about 8 to about 16 carbonatoms; fluorinated linear or branched alkyl radicals having from about 1to about 10 carbon atoms; chlorinated linear or branched alkyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkenyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkenyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkenyl radicals having from about 1 to about 10 carbon atoms;fluorinated linear or branched alkynyl radicals having from about 1 toabout 10 carbon atoms; chlorinated linear or branched alkynyl radicalshaving from about 1 to about 10 carbon atoms; brominated linear orbranched alkynyl radicals having from about 1 to about 10 carbon atoms;hydrocarbonoxy radicals containing at least two carbon atoms;fluorinated hydrocarbonoxy radicals containing at least two carbonatoms; chlorinated hydrocarbonoxy radicals containing at least twocarbon atoms; brominated hydrocarbonoxy radicals containing at least twocarbon atoms aryl radicals; linear or branched alkyl aryl radicals;fluorinated aryl radicals; chlorinated aryl radicals; brominated arylradicals; fluorinated linear or branched alkyl-, alkenyl-, or alkynylaryl radicals; chlorinated linear or branched alkyl-, alkenyl-, oralkynyl aryl radicals; brominated linear or branched alkyl-, alkenyl-,or alkynyl aryl radicals; and triorganosilyl radicals; and v) R isselected from the group consisting of: hydrogen; alkyl; phenyl; andC_(x)H_(y), where x is an integer from about 2 to about 10, and y is aninteger from about 4 to about
 21. 26. A molded silicone rubber articleproduced by using a liquid silicone rubber base comprising: a) at leastone vinyl siloxane polymer; b) at least one hydride crosslinker; c) atleast one filler; d) at least one pre-structuring compound; e) at leastone release agent; and f) optionally, at least one injection moldinginhibitor; but g) no catalyst.